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I love everything about the move to Apple Silicon with the exception of the decision to put memory on-die or in-package (not sure how it is configured). They ca

I love everything about the move to Apple Silicon with the exception of the decision to put memory on-die or in-package (not sure how it is configured). They call it 'Unified Memory'. It makes a lot of sense but I don't know if they are going to be able to pack enough memory in there. A lot of folks are fixated on CPU performance lately (which is rad) but I think that there is a tendency to ignore memory. I have 32gb of RAM on my Macbook Pro and finally feel like it has enough. You can't get an M1 configuration right now larger than 16GB which is a table-stakes baseline dev requirement today.

TylerE 6y ago
I wonder if the CPU can support mixed RAM. E.g. have the on-die 8GB of "fast" ram, and then support 2 external DIMMs or something for "overflow", file caching, etc.
- whalesalad 6y ago
  That is a great idea. I think the software is going to be the hard part. You would need some kind of heuristic or software to manage moving memory between those two locations. That is just my initial thought I could be totally wrong.
  - mutatio 6y ago
    Maybe the memory controller could handle this, spilling onto the slower memory, much like swapping.
  - kemiller 6y ago
    The same logic they already use for L1/L2 caching, and/or VM could pretty easily be adapted.
  - trillic 6y ago
    Every modern general purpose computer already has multiple layers of memory. This would just be an additional layer. The virtual memory subsystems in the OS will handle this. At the end of the day it's just caches all the way down. A workstation with 16GiB of "on-chip" memory would be like a huge L4 cache for the say 512GiB of "standard" DDR4. I really like OSTEP's chapters on virtual memory if you're interested in reading more[1]. [1] http://pages.cs.wisc.edu/~remzi/OSTEP/vm-complete.pdf http://pages.cs.wisc.edu/~remzi/OSTEP/vm-complete.pdf
    - whalesalad 6y ago
      Thanks for the link, downloaded to read this evening :thumbsup:
    - nakkijono 6y ago
      Yet, is it a requirement in a memory hierarchy to copy the lower level in the upper one? Like, all the stuff in you L1 cache has to be also in your L2 cache. E.g. if you would have 32gb of external DDR it would add only 16gb more to the packaged 16gb?
      - sveiss 6y ago
        It's not a requirement, and different systems in the past have made different choices. https://en.wikipedia.org/wiki/Cache_inclusion_policy https://en.wikipedia.org/wiki/Cache_inclusion_policy
      - scottlamb 6y ago
        It's definitely not, and in fact swap on a modern OS doesn't work that way. Something can be only in physical RAM, only in swap, or (when "clean"/unmodified vs the copy in swap) in both (allowing it to be dropped from physical RAM quickly). So one obvious approach would be to simply use the external RAM as swap. Relatedly, I've heard of using Intel Optane as "slow RAM" for cold pages, and I think the idea there is also that it'd be in one or the other but not both. (Optane can be thought of as very expensive/fast flash or very slow/cheap RAM.)
  - codys 6y ago
    macos already has capabilities for compressing memory used by applications before finally giving up and paging it out. It seems plausible they could extend the code that supports that feature to push memory to external (or allocate it there in the first place if utilization isn't expected to be hot), and only pull it back after utilization indicates there is a benefit.
  - usefulcat 6y ago
    Pretty sure this is already a thing for NUMA systems, e.g. an Intel system with a pair of N-core processors. Each processor gets "its own" half of memory. Memory which belongs to the other processor is slower to access. See also Linux cpusets (cset command), which can be used to control which NUMA nodes a process has access to.
  - quasse 6y ago
    Luckily that's a problem that academics have been working on since the 1960s. https://en.wikipedia.org/wiki/Non-uniform_memory_access https://en.wikipedia.org/wiki/Non-uniform_memory_access You'd be surprised how many modern OSes are at least partially NUMA aware. Even Java already has a non-uniform aware allocator.
DonaldPShimoda 6y ago
Keep in mind that so far Apple has only started offering M1 on what are essentially entry-level computers. I think it's likely there will be a 32GB Unified Memory version for the 16" MBP (which maybe will become available on the 13" or Mac Mini too). I think M1 would not be able to achieve the performance and efficiency improvements if the RAM were not integrated, so they'll stick with Unified Memory for the time being. I don't think this will be as tenable for the Mac Pro (and maybe not even iMac Pro), but those are probably much further from Apple Silicon than anything else, so we'll see what happens.
- whalesalad 6y ago
  I agree with you completely. I am looking forward to the next offering and hope that they have a plan for more memory. In the meantime I wonder if they are going to do dual (or more) socket configurations. I was just thinking to myself imagine a Mac Pro with 8 of these M1 chips in it all cooled by one big liquid heat block. That thing would rip.
  - DonaldPShimoda 6y ago
    > hope that they have a plan for more memory. I can't imagine them not doing it. If they were satisfied that 16GB was sufficient, I would've expected them to also refresh the 16" MBP with M1. I think the fact that they didn't is a good indicator that something about M1 isn't ready for the big boy league, and my guess is RAM will factor into that. My guess is that the second generation (M2?) will improve performance with little efficiency gain and will include up to 32GB "Unified Memory". And then binning will be used to produce the 16GB and 8GB variants. > I wonder if they are going to do dual (or more) socket configurations. Whoa, that's something I hadn't thought of! I wonder if M1 is amenable to that kind of configuration. That would be pretty neat!
    - arpigartigar 6y ago
      (This should be a reply to an older comment of yours and I realise it's probably bad form to be posting it here, but I couldn't find any other way to contact you) A few weeks ago you made a comment (https://news.ycombinator.com/item?id=24653498 https://news.ycombinator.com/item?id=24653498) where you mentioned a PL Discord server. Could I get an invite? I can be reached through aa.santos at campus.fct.unl.pt if you'd rather not discuss it in public/if you'd like to verify my identity. Sorry to everyone else in the thread for being off-topic.
andy_ppp 6y ago
Is the new architecture better or worse with memory usage than x86 macs?
- zerkten 6y ago
  Memory usage shouldn't change that much for a similar task. It's just that paging stuff in and out is much more performant when the system is under pressure. Right now with the least amount of M1 native software available, most of it will be allocating memory natively without garbage collection. Apple's strategy has been to avoid generational/tracing GC which reaps big benefits in terms of memory usage. It'll be interesting to see more feedback from devs running a broader range of software. It's likely people will hit apps on the long tail that use GC, and similar schemes, which will cause them to complain about memory issues. Running old apps under Rosetta 2 will be another source of complaints. These machines are optimized for the mass market. Although they can out perform many existing machines with 8 and 16 GB of RAM, there is the huge opportunity and demand for 32GB+.
jug 6y ago
It's a radical decision yes, but also so very Apple-like. And I wonder how much of this wild architecture change is also behind the improved performance here.
kemiller 6y ago
My guess is that they are releasing the M1 right now because it's the smallest SoC they're going to make and its yields are just barely enough to be viable. Once they get better yields on the 5nm process, they will start making the larger, more yield-sensitive SoCs with more RAM in them.
- jeffbee 6y ago
  I don't think that makes any sense, considering that the RAM is not on the same die as the processor. It's on the module, yes, but they're not making it on the same process. I realize this image is a schematic representation rather than an actual photograph, but here it is. https://www.apple.com/v/mac/m1/a/images/overview/chip__fffqz3ljssi2_large.jpg https://www.apple.com/v/mac/m1/a/images/overview/chip__fffqz...
  - psds2 6y ago
    The point being made is that the processors that they will package with more memory are going to exist on larger dies. When you increase die size you decrease yield so you need to have a mature process.
    - jeffbee 6y ago
      Why does that follow? 4 cores and 32GB makes fine sense.
      - zeusk 6y ago
        It's actually 8 core, 4 big (Fire) and 4 small (Ice)
      - psds2 6y ago
        But why would you offer your i3 with 32GB when you know you are going to make i5 and i7 processors soon? Apple could offer 32GB here but choose to not offer every configuration at every level.
    - scottlamb 6y ago
peteradio 6y ago
What uses most of your ram when you need 16GB+?
- whalesalad 6y ago
  You can never have enough ram!
  - peteradio 6y ago
    Haha! I somehow became sated with 16GB on my laptop. Now any of my workloads which require more would simultaneously want higher cpu, so those loads get pushed to a different machine entirely. So I'm curious what is the use case for 16GB+ with a laptop cpu.
    - kilburn 6y ago
      For some people the main advantage of a laptop is the posssibility to move to spots where there's no or very bad connection. In those cases it becomes really useful to be able to run all your workloads on it, even if much slower.
- DoofusOfDeath 6y ago
  For some projects, linking non-stripped binaries can take huge amounts of virtual memory. At least on ELF/DWARF platforms with the Gnu linker. Not sure if that applies here, since I assume the Mac will be using the LLVM linker, and Mach-O != ELF.
  - yjftsjthsd-h 6y ago
    Virtual memory, or real memory? You're never going to run out of virtual memory on a 64-bit platform.
    - DoofusOfDeath 6y ago
      Virtual memory. I mentioned it in this context because running out of physical memory means the machine starts swapping, which often results in a very undesirable slowdown.
tannhaeuser 6y ago
Isn't fast on-die/on-package (not sure either) memory access a key factor for Apple's gigantic performance leap, though? With memory pre-soldered on small notebooks for years now, it's not much of a difference for consumers anyway once more than 16GB becomes available.
- deleted 6y ago
  [deleted]
- epistasis 6y ago
  I'm not sure that the soldering does much to improve memory access. The anand tech M1 article measures memory latency at more than 90ns [1], which is almost twice what I see for AMD and Intel benchmarks, at 50ns and 70ns [2]. If these are not comparable measurements, I'd love a correction! It seems to me that there's significant room to improve the memory subsystem for Apple Silicon to reach parity with desktop RAM performance. [1] https://www.anandtech.com/show/16252/mac-mini-apple-m1-tested https://www.anandtech.com/show/16252/mac-mini-apple-m1-teste... [2] https://www.techcenturion.com/improve-zen-2-gaming-performance https://www.techcenturion.com/improve-zen-2-gaming-performan...
schultzer 6y ago
What people seam to forget is, that SOC is the future, and an upgrade should be as simple as switching one chip. This also comes with a lot of benefit with locality and performance.
- timw4mail 6y ago
  There's no way the SOC will be upgradable.
  - redisman 6y ago
    No - but for desktop maybe that's the future? I could imagine AMD and Intel offering multiple tiers of SoCs instead of CPUs.
    - leptons 6y ago
      No. That's a stupid idea for desktop. Not everyone needs 64GB of RAM, but some of us do - and that would be an expensive and awful upgrade to have to throw out your CPU with 32GB RAM on-chip just to put in the same CPU with 64GB on-chip. It makes absolutely no sense.
      - robotresearcher 6y ago
        I'd tolerate that if it runs usefully faster every day. Could save money overall. There are several parts in a workstation that are already monolithic packages. Most GPU+GRAM cards, for example.
        leptons 6y ago
        So you're talking about taking a $300 CPU chip and turning into a $500 or $800 chip depending on how much RAM is on the SOC. But the fact still remains that the vast majority of the RAM sits idle while the CPU processes through relatively small chunks of it at a time, which is what cache is for. If anything I'd rather see more cache RAM on the CPU itself than having to pay for a CPU + RAM on the same SOC. The performance gain from combining CPU + RAM on the same "SOC" is not that great enough to warrant doing that as an approach for all computers - Apple is doing this mostly because it saves them money. There's a lot of push back from power users about expandability not even being an option anymore. But 99% of Apple's customer base doesn't have any need for expandability or power-user features, or having the fastest silicon available because they only use it for facebook, facetime, or a few other basic applications. And that's fine. I won't be buying one though.
jeffbee 6y ago
I agree completely since for large projects 16GB is barely enough to run Bazel. I know that's kind of sad but often Bazel wants to load large graphs into memory. Combined with the fact that the graphics are stealing part of main memory, I don't think I'm going to be happy with 16GB. I ordered one anyway, but I don't expect to be too psyched about the reality of it when it gets here.
- mixmastamyk 6y ago
  Sounds like the build needs to be optimized.
djsumdog 6y ago
Not to mention the e-waste and the inability for users to upgrade their own devices. I wonder what the performance cost was of having standard memory modules. I suspect it wasn't significant and this is more of a move to prevent upgrade and increase consumption and waste. This is another reason I really don't ever want to own another Apple device. They want more and more control over the system and they keep moving to policies that reduce the ability of regular people to repair. The performance benefit doesn't really seem worth it if I can't run any other operating systems except macOS on it.
- gjsman-1000 6y ago
  Even if you could boot other OSs, you forget that there are no drivers written for them. Windows and Linux both would be unusable for potentially years after launch.
  - yjftsjthsd-h 6y ago
    It would certainly help if Apple would release specs, or even just liberally-licensed XNU driver sources, but Linux has certainly gotten drivers without manufacturer help before.
- spijdar 6y ago
  Standard memory modules which were soldered onto the mainboard? Given how Macbooks have had soldered memory packages for ... 8 years now, I don't think moving the memory onto the SoC was to lock out upgrade potential. It doesn't make upgrading any less possible than "completely impossible", and probably (slightly) reduces the overall cost/complexity of the board, slightly reducing the material cost/impact. FWIW, in the future I imagine most processors will look like the M1, with additional memory available over a serial bus like OMI, used in POWER10. The "unified memory" will effectively serve as a giant cache for the CPU/GPU with slower peripheral memory used as a backing store.
stefan_ 6y ago
It's not magic memory, it's LPDDR4X-4266 or LPDDR5-5500. These work just fine without being in-package, so it's purely a cost cutting decision.
- scottlamb 6y ago
  That's a pretty significant step up from what they were previously shipping, right? The 16" MBP page says it has "2666MHz DDR4". Are any other major (laptop or desktop) manufacturers using LPDDR4X-4266 or LPDDR5-5500?
dom96 6y ago
I actually feel like 16GB is pretty much the sweet spot. I've built a desktop PC recently and didn't bother with 32GB and haven't had any troubles. The only time I've run into limits is when I was doing things like running games and big IDEs at the same time which seems like a waste in any case regardless of how much RAM is available.
- phren0logy 6y ago
  I would agree if it wasn't doing double-duty as memory for the GPU. Under those circumstances, even 16gb can start to get a bit tight on some tasks.
- nullandvoid 6y ago
  For me on windows, multiple virtual desktops, browser (chrome for work, ff for personal) IDE's and VMs (ubuntu running in wsl, and any docker containers) made 16gn unuseable for me And that's before I decided to boot up a game with all of the existing applications For me the £50 is well worth not having to care about pruning applications constantly!
  - vmception 6y ago
    I recently got introduced to great suspender here and Chrome with separate accounts doesn't use much resources because tabs get backgrounded. Yes, you would still have to juggle if you really dont want to close your IDE, or lower judge how much RAM that docker container really needd, but also understand that OS’ and software allocate a huge portion of all available memory no matter what you have in the machine. Like you think you need 32gb for snappy performance and it is rational idea that all your processes absolutely need sequential memory blocks, but it isnt that true. I honestly think you would just be smarter about your use of resources again. With these benchmarks I am starting to lean more towards 32gb itself being the compromise. Simply because it doesnt cause you to budget resources, a luxury, but at the expense of these other benchmarks? And in the worst case we just have to wait a year or two before 32gb is offered in the M series package?
  - spullara 6y ago
    I wonder if they have improved their memory compression with this new release as well. Would have compare apples to apples for various applications to see the effect.
ogre_codes 6y ago
> You can't get an M1 configuration right now larger than 16GB which is a table-stakes baseline dev requirement today. Everyone on my team has been using 15" MacBook Pros with 16GB RAM for the past 3 years. I suspect most developers run with 16GB of RAM just fine. I'm not arguing "16GB is fine for all developers everywhere!", but it's absolutely not a hard requirement. I suspect for a lot of us, the difference in performance between 16GB and 32GB is trivial. Regardless, the thing which is kind of stunning about this chip is that they are getting this kind of performance out of what is basically their MacBook Air CPU. Follow on CPUs—which will almost certainly support 32GB RAM—will likely be even faster.
- whalesalad 6y ago
  I think if you have a very specific role where your workload is constant it makes sense. I am an independent contractor and work across a lot of different projects. Some of my client projects require running a full Rails/Worker/DB/Elasticsearch/Redis stack. Then add in my dev tools, browser windows, music, Slack, etc... it adds up. If I want to run a migration for one client in a stack like that and then want to switch gears to a different project to continue making progress elsewhere I can do that without shutting things down. Running a VM for instance ... I can boot a VM with a dedicated 8GB of ram for itself without compromising the rest of my experience. That is why I think 16GB is table stakes. It is the absolute minimum anyone in this field should demand in their systems. Honestly the cost of more RAM is pretty much negligible. If I am buying laptops for a handful of my engineers I am surely going to spend $200x5 or whatever the cost is once to give them all an immediate boost. Cost/benefit is strong for this.
  - tempest_ 6y ago
    At some point it is easier to have something sitting in a rack somewhere. That way you dont have to cook your ultrabook to run that stuff.
    - ogre_codes 6y ago
      People have been saying this kind of thing for years, but so far it doesn't really math out. Having a CPU "in the cloud" is usually more expensive and slower than just using cycles on the CPU which is on your lap. The economics of this hasn't changed much over the past 10 years and I doubt it's going to change any time soon. Ultimately local computers will always have excess capacity because of the normal bursty nature of general purpose computing. It makes more sense to just upscale that local CPU than to rent a secondary CPU which imposes a bunch of network overhead. There are definitely exceptions for things which require particularly large CPU/ GPU loads or particularly long jobs, but most developers will running local for a long time to come. CPUs like this just make it even more difficult for cloud compute to be make economic sense.
minimalist 6y ago
Perhaps this will encourage programmers to write true native applications again instead of wrapping web scripting languages in a browser and calling it a day.
- yborg 6y ago
  I'd say the opposite, this increases the speed of such apps to closer to what is now native speed.
  - minimalist 6y ago
    I'm referring to the second point about memory that OP made. You know, having to allocate 700MB of memory in order to run an electron chat application.
    - bufferoverflow 6y ago
      It's seems wasteful, but RAM is so cheap, who cares? You can get 16GB for $52 on Amazon. That 700MB is equivalent to $4.64 one-time payment. There are more important things to worry about, seems to me.
      - minimalist 6y ago
        Not everyone lives in the first world. Not everyone has a new computer. It is this sort of hubris that likely explains my feeling that personal computing has regressed in many ways for the average individual over the recent years. I'm not talking about the hacker who can run surf+i3 on their cyberdeck, I'm talking about the person with an 8-year old computer bought on sale or a 4-year old smartphone.
      - imtringued 6y ago
        RAM is only cheap because people don't waste it. If every application was written with Electron or every executable was a Java program (including CLI commands) you would cry and beg for more memory efficiency.
    - 6y ago
heisenbergs 6y ago
According to anandtech the memory throughput is off the charts at 68.25GB/s [1]. That's twice as fast as high speed ddr4 memory (DDR4-4000 at 32GB/s). In other words: they totally trounced and took it to the next level with regards to memory, because they can. If anything, memory control is their biggest advantage. Scaling the amount of ram won't be an issue. Increasing the bandwidth perhaps, but it'll still be way quicker than what Intel or AMD offer. This seems like something their next gen M2 version could tackle as a somewhat low hanging fruit. [1] https://www.anandtech.com/show/16252/mac-mini-apple-m1-tested https://www.anandtech.com/show/16252/mac-mini-apple-m1-teste...
- masklinn 6y ago
  FWIW the latest-gen consoles supposedly have memory bandwidth in the hundreds of GB/s. The PS5 supposedly reaches 448GB/s, and the XBX 336 to 560 depending on the memory segment.
  - redisman 6y ago
    It's the year of system-on-chip. It does show great improvements at the trade-off cost of no expansions possible once the chip is made.
    - masklinn 6y ago
      None of these systems seem to have on-die memory. Not sure about the XBS, but from the official teardown the PS5 doesn't even use on-package memory: https://www.gamereactor.eu/media/87/_3278703.png https://www.gamereactor.eu/media/87/_3278703.png And Apple certainly didn't wait for SoC to use soldered memory.
- wmf 6y ago
  Tiger Lake appears to have the same bandwidth at the chip level but AnandTech is using inconsistent methodology so it's not clear.
- sfblah 6y ago
  Isn't that just because all the memory is on the CPU?
masklinn 6y ago
> They call it 'Unified Memory'. It makes a lot of sense but I don't know if they are going to be able to pack enough memory in there. Unified memory and on-die (or in-package) memory are different thing, and while the latter simplifies the former they're mostly orthogonal. Unified memory means the physical and logical memory space is directly accessible by both CPU and GPU, at the same time, in their entirety: https://en.wikipedia.org/wiki/Heterogeneous_System_Architecture#Block_diagrams https://en.wikipedia.org/wiki/Heterogeneous_System_Architect...
sudhirj 6y ago
One, this is repeating the iPhone vs Android comparisons. iPhones with 4GB RAM feel faster and get more work done than Androids running Qualcomm ARM with double that amount of RAM. The faster IO becomes the cheaper paging becomes, and macOS and iOS have a lot of work done to handle paging well. Two, this is the entry level processor, made for the Air, which is what we get for students, non-technical family members and spare machines. Let’s see what the “pro” version of this is, the M1X or whatever. We already know this chip isn’t going to go as is into the 16 inch MacBook Pro, the iMac Pro or the Mac Pro. I’d like to see what comes in those boxes.
- aunetx 6y ago
  I may be wrong, but the ecosystem does not really change here right? I mean, memory management should be roughly the same between x86_64 and arm regarding the amount of ram used, so I guess 16gb of ram under old macbooks is the same as 16gb under the new ones
  - sudhirj 6y ago
    All else being equal, yes, but the memory is faster, closer to the chip, has less wiring to go through, and because of vertical integration they can pass by reference instead of copying values internally on the hardware. The last one is big - because all the parts of the SoC trust each other and work together they can share memory withing having to copy data over the bus. That coupled with superfast SSDs means that comparisons aren't Apples to oranges, excuse the pun. 16GB of memory on-die shared by all the components of an SoC is not the same as 16GB made available to separate system components, each of which will attempt to jealously manage their own copy of all data.
    - kcartlidge 6y ago
      I'm not a hardware person, but I do software for a living. Your comment makes things much clearer. You're saying that the effective difference in having the shared memory is that you get more data passed by reference and not by value at the lower levels? If that's true, then you get extra throughput by only moving references around instead of shuffling whole blocks of data, and you also gain better resource usage by having the same chunks of allocated memory being shared rather than duplicated across components?
deleted 6y ago
[deleted]
gumby 6y ago
> memory on-die or in-package (not sure how it is configured). They call it 'Unified Memory' It’s in the package; RAM on the die is called “cache”. “Unified memory” has nothing to do with packaging. It’s the default for how computer memory has worked since, well, the 1950s: all the parts talk to the same pool of memory (and you can DMA data for any device). That’s why the term of art for, say, GPUs having their own memory, is called NUMA (“Non-Uniform Memory Access”): unified is the default.) * M1 is a remarkable chip and Apple doesn’t claim that UFA is some invention: they just used the technical term, just as they say their chips use doped silicon gates. It has become unusual these days and worth their mentioning, but it’s simply ignorance by the reporters that elevated it to seem like some brand name. * https://en.wikipedia.org/wiki/Non-uniform_memory_access https://en.wikipedia.org/wiki/Non-uniform_memory_access
- Symmetry 6y ago
  In a NUMA system all the memory is in the same address space even if it's faster for a core to talk to some places than other. Traditionally GPUs work in a completely different address space and doesn't use virtual memory. Yes you can DMA to it but if you DMA a pointer it will break on the other end.
herf 6y ago
Anandtech is reporting 62GB/sec memcpy, and the way-faster Geekbench results are the memory-bound ones (e.g., Gaussian blur is 4x faster!) So I think the speedups like these are largely due to memory architecture.
- mikechen233 6y ago
  It's not due to the on package or the united memory. M1 is using industry standard 128bits lpddr4. On package is still using regular dram chips. What seemingly is the advantage is the firestorm cpu has much wider pipeline and capable doing more load and store in-flight at the time. Also the cache is also able to provide low latency and the bandwidth numbers. Intel or amd is able to achieve similar performance in memory bound workloads if they designed the logic on cpu for that workload.
pwinnski 6y ago
Putting the memory into the SoC seems to be a lot of how they're getting this amazing performance: the memory bus is now twice as wide as anything else. But yes, it means that Apple is going to have to either really start jamming more and more into there, or develop a two-tiered approach to memory where slower "external" RAM can supplement the faster "internal" RAM.
- wmf 6y ago
  The memory bus is now the same width as every other laptop.
Eric_WVGG 6y ago
I'm afraid I lost the source, but this morning I was reading about some fairly in-depth Xcode benchmarks, the dev was saying that there was almost no hit in performance when it hit swap, and speculated that Apple might be getting ready to move past the concept of RAM altogether in a few years. Sounds a little bonkers to me, but the bus to the SSD is no joke
- mikechen233 6y ago
  Next gen consoles and Nvidia rtx io is kind of doing that with graphics textures. Textures are memory mapped but stored in nvme storage. When GPU reads a texture, it first looks in the ram, if not found in the ram, the controller talks to nvme controllers to load from storage. If you think about it, gen4 pce nvme can reach 5GB/s doing 16k ramdom reads. The bandwidth is getting close to ddr2/3 territory. And new storage tech like 3dxpoint will have ram like access latency to improve small io perf. You will always still need ram, but you can be more efficient at how to use the ram.
- deleted 6y ago
  [deleted]
- Eric_WVGG 6y ago
  here's the source of that comment: https://twitter.com/panzer/status/1328708737482121217?s=21 https://twitter.com/panzer/status/1328708737482121217?s=21 I'm still a little unclear on whether he means "concept of RAM" in a marketing sense, discrete RAM, or a model closer to L3 cache. regardless, pure speculation
Symmetry 6y ago
It's certainly in package rather than on the same chip. The process required to make DDR is different from what you use to make the core's logic. The DRAM chips might be literally stack on top of the CPU chip, though. Apple does things that way in the iPhone IIRC.
jjtheblunt 6y ago
Maybe ARM binaries are smaller than x86_64? ARM has some sophistication in its ISA, THUMB mode instructions for example, that might be in play here.
- duskwuff 6y ago
  Thumb isn't a factor. The Thumb encoding is only used for 32-bit ARM instructions; 64-bit instructions use a fixed-width 32-bit encoding.

TylerE 6y ago

I wonder if the CPU can support mixed RAM. E.g. have the on-die 8GB of "fast" ram, and then support 2 external DIMMs or something for "overflow", file caching, etc.

whalesalad 6y ago
That is a great idea. I think the software is going to be the hard part. You would need some kind of heuristic or software to manage moving memory between those two locations. That is just my initial thought I could be totally wrong.
- mutatio 6y ago
  Maybe the memory controller could handle this, spilling onto the slower memory, much like swapping.
- kemiller 6y ago
  The same logic they already use for L1/L2 caching, and/or VM could pretty easily be adapted.
- trillic 6y ago
  Every modern general purpose computer already has multiple layers of memory. This would just be an additional layer. The virtual memory subsystems in the OS will handle this. At the end of the day it's just caches all the way down. A workstation with 16GiB of "on-chip" memory would be like a huge L4 cache for the say 512GiB of "standard" DDR4. I really like OSTEP's chapters on virtual memory if you're interested in reading more[1]. [1] http://pages.cs.wisc.edu/~remzi/OSTEP/vm-complete.pdf http://pages.cs.wisc.edu/~remzi/OSTEP/vm-complete.pdf
  - whalesalad 6y ago
    Thanks for the link, downloaded to read this evening :thumbsup:
  - nakkijono 6y ago
    Yet, is it a requirement in a memory hierarchy to copy the lower level in the upper one? Like, all the stuff in you L1 cache has to be also in your L2 cache. E.g. if you would have 32gb of external DDR it would add only 16gb more to the packaged 16gb?
    - sveiss 6y ago
      It's not a requirement, and different systems in the past have made different choices. https://en.wikipedia.org/wiki/Cache_inclusion_policy https://en.wikipedia.org/wiki/Cache_inclusion_policy
    - scottlamb 6y ago
      It's definitely not, and in fact swap on a modern OS doesn't work that way. Something can be only in physical RAM, only in swap, or (when "clean"/unmodified vs the copy in swap) in both (allowing it to be dropped from physical RAM quickly). So one obvious approach would be to simply use the external RAM as swap. Relatedly, I've heard of using Intel Optane as "slow RAM" for cold pages, and I think the idea there is also that it'd be in one or the other but not both. (Optane can be thought of as very expensive/fast flash or very slow/cheap RAM.)
- codys 6y ago
  macos already has capabilities for compressing memory used by applications before finally giving up and paging it out. It seems plausible they could extend the code that supports that feature to push memory to external (or allocate it there in the first place if utilization isn't expected to be hot), and only pull it back after utilization indicates there is a benefit.
- usefulcat 6y ago
  Pretty sure this is already a thing for NUMA systems, e.g. an Intel system with a pair of N-core processors. Each processor gets "its own" half of memory. Memory which belongs to the other processor is slower to access. See also Linux cpusets (cset command), which can be used to control which NUMA nodes a process has access to.
- quasse 6y ago
  Luckily that's a problem that academics have been working on since the 1960s. https://en.wikipedia.org/wiki/Non-uniform_memory_access https://en.wikipedia.org/wiki/Non-uniform_memory_access You'd be surprised how many modern OSes are at least partially NUMA aware. Even Java already has a non-uniform aware allocator.

DonaldPShimoda 6y ago

Keep in mind that so far Apple has only started offering M1 on what are essentially entry-level computers. I think it's likely there will be a 32GB Unified Memory version for the 16" MBP (which maybe will become available on the 13" or Mac Mini too). I think M1 would not be able to achieve the performance and efficiency improvements if the RAM were not integrated, so they'll stick with Unified Memory for the time being. I don't think this will be as tenable for the Mac Pro (and maybe not even iMac Pro), but those are probably much further from Apple Silicon than anything else, so we'll see what happens.

whalesalad 6y ago
I agree with you completely. I am looking forward to the next offering and hope that they have a plan for more memory. In the meantime I wonder if they are going to do dual (or more) socket configurations. I was just thinking to myself imagine a Mac Pro with 8 of these M1 chips in it all cooled by one big liquid heat block. That thing would rip.
- DonaldPShimoda 6y ago
  > hope that they have a plan for more memory. I can't imagine them not doing it. If they were satisfied that 16GB was sufficient, I would've expected them to also refresh the 16" MBP with M1. I think the fact that they didn't is a good indicator that something about M1 isn't ready for the big boy league, and my guess is RAM will factor into that. My guess is that the second generation (M2?) will improve performance with little efficiency gain and will include up to 32GB "Unified Memory". And then binning will be used to produce the 16GB and 8GB variants. > I wonder if they are going to do dual (or more) socket configurations. Whoa, that's something I hadn't thought of! I wonder if M1 is amenable to that kind of configuration. That would be pretty neat!
  - arpigartigar 6y ago
    (This should be a reply to an older comment of yours and I realise it's probably bad form to be posting it here, but I couldn't find any other way to contact you) A few weeks ago you made a comment (https://news.ycombinator.com/item?id=24653498 https://news.ycombinator.com/item?id=24653498) where you mentioned a PL Discord server. Could I get an invite? I can be reached through aa.santos at campus.fct.unl.pt if you'd rather not discuss it in public/if you'd like to verify my identity. Sorry to everyone else in the thread for being off-topic.

andy_ppp 6y ago

Is the new architecture better or worse with memory usage than x86 macs?

zerkten 6y ago
Memory usage shouldn't change that much for a similar task. It's just that paging stuff in and out is much more performant when the system is under pressure. Right now with the least amount of M1 native software available, most of it will be allocating memory natively without garbage collection. Apple's strategy has been to avoid generational/tracing GC which reaps big benefits in terms of memory usage. It'll be interesting to see more feedback from devs running a broader range of software. It's likely people will hit apps on the long tail that use GC, and similar schemes, which will cause them to complain about memory issues. Running old apps under Rosetta 2 will be another source of complaints. These machines are optimized for the mass market. Although they can out perform many existing machines with 8 and 16 GB of RAM, there is the huge opportunity and demand for 32GB+.

jug 6y ago

It's a radical decision yes, but also so very Apple-like. And I wonder how much of this wild architecture change is also behind the improved performance here.

kemiller 6y ago

My guess is that they are releasing the M1 right now because it's the smallest SoC they're going to make and its yields are just barely enough to be viable. Once they get better yields on the 5nm process, they will start making the larger, more yield-sensitive SoCs with more RAM in them.

jeffbee 6y ago
I don't think that makes any sense, considering that the RAM is not on the same die as the processor. It's on the module, yes, but they're not making it on the same process. I realize this image is a schematic representation rather than an actual photograph, but here it is. https://www.apple.com/v/mac/m1/a/images/overview/chip__fffqz3ljssi2_large.jpg https://www.apple.com/v/mac/m1/a/images/overview/chip__fffqz...
- psds2 6y ago
  The point being made is that the processors that they will package with more memory are going to exist on larger dies. When you increase die size you decrease yield so you need to have a mature process.
  - jeffbee 6y ago
    Why does that follow? 4 cores and 32GB makes fine sense.
    - zeusk 6y ago
      It's actually 8 core, 4 big (Fire) and 4 small (Ice)
    - psds2 6y ago
      But why would you offer your i3 with 32GB when you know you are going to make i5 and i7 processors soon? Apple could offer 32GB here but choose to not offer every configuration at every level.
  - scottlamb 6y ago

peteradio 6y ago

What uses most of your ram when you need 16GB+?

whalesalad 6y ago
You can never have enough ram!
- peteradio 6y ago
  Haha! I somehow became sated with 16GB on my laptop. Now any of my workloads which require more would simultaneously want higher cpu, so those loads get pushed to a different machine entirely. So I'm curious what is the use case for 16GB+ with a laptop cpu.
  - kilburn 6y ago
    For some people the main advantage of a laptop is the posssibility to move to spots where there's no or very bad connection. In those cases it becomes really useful to be able to run all your workloads on it, even if much slower.
DoofusOfDeath 6y ago
For some projects, linking non-stripped binaries can take huge amounts of virtual memory. At least on ELF/DWARF platforms with the Gnu linker. Not sure if that applies here, since I assume the Mac will be using the LLVM linker, and Mach-O != ELF.
- yjftsjthsd-h 6y ago
  Virtual memory, or real memory? You're never going to run out of virtual memory on a 64-bit platform.
  - DoofusOfDeath 6y ago
    Virtual memory. I mentioned it in this context because running out of physical memory means the machine starts swapping, which often results in a very undesirable slowdown.

tannhaeuser 6y ago

Isn't fast on-die/on-package (not sure either) memory access a key factor for Apple's gigantic performance leap, though? With memory pre-soldered on small notebooks for years now, it's not much of a difference for consumers anyway once more than 16GB becomes available.

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epistasis 6y ago
I'm not sure that the soldering does much to improve memory access. The anand tech M1 article measures memory latency at more than 90ns [1], which is almost twice what I see for AMD and Intel benchmarks, at 50ns and 70ns [2]. If these are not comparable measurements, I'd love a correction! It seems to me that there's significant room to improve the memory subsystem for Apple Silicon to reach parity with desktop RAM performance. [1] https://www.anandtech.com/show/16252/mac-mini-apple-m1-tested https://www.anandtech.com/show/16252/mac-mini-apple-m1-teste... [2] https://www.techcenturion.com/improve-zen-2-gaming-performance https://www.techcenturion.com/improve-zen-2-gaming-performan...

schultzer 6y ago

What people seam to forget is, that SOC is the future, and an upgrade should be as simple as switching one chip. This also comes with a lot of benefit with locality and performance.

timw4mail 6y ago
There's no way the SOC will be upgradable.
- redisman 6y ago
  No - but for desktop maybe that's the future? I could imagine AMD and Intel offering multiple tiers of SoCs instead of CPUs.
  - leptons 6y ago
    No. That's a stupid idea for desktop. Not everyone needs 64GB of RAM, but some of us do - and that would be an expensive and awful upgrade to have to throw out your CPU with 32GB RAM on-chip just to put in the same CPU with 64GB on-chip. It makes absolutely no sense.
    - robotresearcher 6y ago
      I'd tolerate that if it runs usefully faster every day. Could save money overall. There are several parts in a workstation that are already monolithic packages. Most GPU+GRAM cards, for example.
      - leptons 6y ago
        So you're talking about taking a $300 CPU chip and turning into a $500 or $800 chip depending on how much RAM is on the SOC. But the fact still remains that the vast majority of the RAM sits idle while the CPU processes through relatively small chunks of it at a time, which is what cache is for. If anything I'd rather see more cache RAM on the CPU itself than having to pay for a CPU + RAM on the same SOC. The performance gain from combining CPU + RAM on the same "SOC" is not that great enough to warrant doing that as an approach for all computers - Apple is doing this mostly because it saves them money. There's a lot of push back from power users about expandability not even being an option anymore. But 99% of Apple's customer base doesn't have any need for expandability or power-user features, or having the fastest silicon available because they only use it for facebook, facetime, or a few other basic applications. And that's fine. I won't be buying one though.

jeffbee 6y ago

I agree completely since for large projects 16GB is barely enough to run Bazel. I know that's kind of sad but often Bazel wants to load large graphs into memory. Combined with the fact that the graphics are stealing part of main memory, I don't think I'm going to be happy with 16GB. I ordered one anyway, but I don't expect to be too psyched about the reality of it when it gets here.

mixmastamyk 6y ago
Sounds like the build needs to be optimized.

djsumdog 6y ago

Not to mention the e-waste and the inability for users to upgrade their own devices. I wonder what the performance cost was of having standard memory modules. I suspect it wasn't significant and this is more of a move to prevent upgrade and increase consumption and waste. This is another reason I really don't ever want to own another Apple device. They want more and more control over the system and they keep moving to policies that reduce the ability of regular people to repair. The performance benefit doesn't really seem worth it if I can't run any other operating systems except macOS on it.

gjsman-1000 6y ago
Even if you could boot other OSs, you forget that there are no drivers written for them. Windows and Linux both would be unusable for potentially years after launch.
- yjftsjthsd-h 6y ago
  It would certainly help if Apple would release specs, or even just liberally-licensed XNU driver sources, but Linux has certainly gotten drivers without manufacturer help before.
spijdar 6y ago
Standard memory modules which were soldered onto the mainboard? Given how Macbooks have had soldered memory packages for ... 8 years now, I don't think moving the memory onto the SoC was to lock out upgrade potential. It doesn't make upgrading any less possible than "completely impossible", and probably (slightly) reduces the overall cost/complexity of the board, slightly reducing the material cost/impact. FWIW, in the future I imagine most processors will look like the M1, with additional memory available over a serial bus like OMI, used in POWER10. The "unified memory" will effectively serve as a giant cache for the CPU/GPU with slower peripheral memory used as a backing store.

stefan_ 6y ago

It's not magic memory, it's LPDDR4X-4266 or LPDDR5-5500. These work just fine without being in-package, so it's purely a cost cutting decision.

scottlamb 6y ago
That's a pretty significant step up from what they were previously shipping, right? The 16" MBP page says it has "2666MHz DDR4". Are any other major (laptop or desktop) manufacturers using LPDDR4X-4266 or LPDDR5-5500?

dom96 6y ago

I actually feel like 16GB is pretty much the sweet spot. I've built a desktop PC recently and didn't bother with 32GB and haven't had any troubles. The only time I've run into limits is when I was doing things like running games and big IDEs at the same time which seems like a waste in any case regardless of how much RAM is available.

phren0logy 6y ago
I would agree if it wasn't doing double-duty as memory for the GPU. Under those circumstances, even 16gb can start to get a bit tight on some tasks.
nullandvoid 6y ago
For me on windows, multiple virtual desktops, browser (chrome for work, ff for personal) IDE's and VMs (ubuntu running in wsl, and any docker containers) made 16gn unuseable for me And that's before I decided to boot up a game with all of the existing applications For me the £50 is well worth not having to care about pruning applications constantly!
- vmception 6y ago
  I recently got introduced to great suspender here and Chrome with separate accounts doesn't use much resources because tabs get backgrounded. Yes, you would still have to juggle if you really dont want to close your IDE, or lower judge how much RAM that docker container really needd, but also understand that OS’ and software allocate a huge portion of all available memory no matter what you have in the machine. Like you think you need 32gb for snappy performance and it is rational idea that all your processes absolutely need sequential memory blocks, but it isnt that true. I honestly think you would just be smarter about your use of resources again. With these benchmarks I am starting to lean more towards 32gb itself being the compromise. Simply because it doesnt cause you to budget resources, a luxury, but at the expense of these other benchmarks? And in the worst case we just have to wait a year or two before 32gb is offered in the M series package?
- spullara 6y ago
  I wonder if they have improved their memory compression with this new release as well. Would have compare apples to apples for various applications to see the effect.

ogre_codes 6y ago

> You can't get an M1 configuration right now larger than 16GB which is a table-stakes baseline dev requirement today. Everyone on my team has been using 15" MacBook Pros with 16GB RAM for the past 3 years. I suspect most developers run with 16GB of RAM just fine. I'm not arguing "16GB is fine for all developers everywhere!", but it's absolutely not a hard requirement. I suspect for a lot of us, the difference in performance between 16GB and 32GB is trivial. Regardless, the thing which is kind of stunning about this chip is that they are getting this kind of performance out of what is basically their MacBook Air CPU. Follow on CPUs—which will almost certainly support 32GB RAM—will likely be even faster.

whalesalad 6y ago
I think if you have a very specific role where your workload is constant it makes sense. I am an independent contractor and work across a lot of different projects. Some of my client projects require running a full Rails/Worker/DB/Elasticsearch/Redis stack. Then add in my dev tools, browser windows, music, Slack, etc... it adds up. If I want to run a migration for one client in a stack like that and then want to switch gears to a different project to continue making progress elsewhere I can do that without shutting things down. Running a VM for instance ... I can boot a VM with a dedicated 8GB of ram for itself without compromising the rest of my experience. That is why I think 16GB is table stakes. It is the absolute minimum anyone in this field should demand in their systems. Honestly the cost of more RAM is pretty much negligible. If I am buying laptops for a handful of my engineers I am surely going to spend $200x5 or whatever the cost is once to give them all an immediate boost. Cost/benefit is strong for this.
- tempest_ 6y ago
  At some point it is easier to have something sitting in a rack somewhere. That way you dont have to cook your ultrabook to run that stuff.
  - ogre_codes 6y ago
    People have been saying this kind of thing for years, but so far it doesn't really math out. Having a CPU "in the cloud" is usually more expensive and slower than just using cycles on the CPU which is on your lap. The economics of this hasn't changed much over the past 10 years and I doubt it's going to change any time soon. Ultimately local computers will always have excess capacity because of the normal bursty nature of general purpose computing. It makes more sense to just upscale that local CPU than to rent a secondary CPU which imposes a bunch of network overhead. There are definitely exceptions for things which require particularly large CPU/ GPU loads or particularly long jobs, but most developers will running local for a long time to come. CPUs like this just make it even more difficult for cloud compute to be make economic sense.

minimalist 6y ago

Perhaps this will encourage programmers to write true native applications again instead of wrapping web scripting languages in a browser and calling it a day.

yborg 6y ago
I'd say the opposite, this increases the speed of such apps to closer to what is now native speed.
- minimalist 6y ago
  I'm referring to the second point about memory that OP made. You know, having to allocate 700MB of memory in order to run an electron chat application.
  - bufferoverflow 6y ago
    It's seems wasteful, but RAM is so cheap, who cares? You can get 16GB for $52 on Amazon. That 700MB is equivalent to $4.64 one-time payment. There are more important things to worry about, seems to me.
    - minimalist 6y ago
      Not everyone lives in the first world. Not everyone has a new computer. It is this sort of hubris that likely explains my feeling that personal computing has regressed in many ways for the average individual over the recent years. I'm not talking about the hacker who can run surf+i3 on their cyberdeck, I'm talking about the person with an 8-year old computer bought on sale or a 4-year old smartphone.
    - imtringued 6y ago
      RAM is only cheap because people don't waste it. If every application was written with Electron or every executable was a Java program (including CLI commands) you would cry and beg for more memory efficiency.
  - 6y ago

heisenbergs 6y ago

According to anandtech the memory throughput is off the charts at 68.25GB/s [1]. That's twice as fast as high speed ddr4 memory (DDR4-4000 at 32GB/s). In other words: they totally trounced and took it to the next level with regards to memory, because they can. If anything, memory control is their biggest advantage. Scaling the amount of ram won't be an issue. Increasing the bandwidth perhaps, but it'll still be way quicker than what Intel or AMD offer. This seems like something their next gen M2 version could tackle as a somewhat low hanging fruit. [1] https://www.anandtech.com/show/16252/mac-mini-apple-m1-tested https://www.anandtech.com/show/16252/mac-mini-apple-m1-teste...

masklinn 6y ago
FWIW the latest-gen consoles supposedly have memory bandwidth in the hundreds of GB/s. The PS5 supposedly reaches 448GB/s, and the XBX 336 to 560 depending on the memory segment.
- redisman 6y ago
  It's the year of system-on-chip. It does show great improvements at the trade-off cost of no expansions possible once the chip is made.
  - masklinn 6y ago
    None of these systems seem to have on-die memory. Not sure about the XBS, but from the official teardown the PS5 doesn't even use on-package memory: https://www.gamereactor.eu/media/87/_3278703.png https://www.gamereactor.eu/media/87/_3278703.png And Apple certainly didn't wait for SoC to use soldered memory.
wmf 6y ago
Tiger Lake appears to have the same bandwidth at the chip level but AnandTech is using inconsistent methodology so it's not clear.
sfblah 6y ago
Isn't that just because all the memory is on the CPU?

masklinn 6y ago

> They call it 'Unified Memory'. It makes a lot of sense but I don't know if they are going to be able to pack enough memory in there. Unified memory and on-die (or in-package) memory are different thing, and while the latter simplifies the former they're mostly orthogonal. Unified memory means the physical and logical memory space is directly accessible by both CPU and GPU, at the same time, in their entirety: https://en.wikipedia.org/wiki/Heterogeneous_System_Architecture#Block_diagrams https://en.wikipedia.org/wiki/Heterogeneous_System_Architect...

sudhirj 6y ago

One, this is repeating the iPhone vs Android comparisons. iPhones with 4GB RAM feel faster and get more work done than Androids running Qualcomm ARM with double that amount of RAM. The faster IO becomes the cheaper paging becomes, and macOS and iOS have a lot of work done to handle paging well. Two, this is the entry level processor, made for the Air, which is what we get for students, non-technical family members and spare machines. Let’s see what the “pro” version of this is, the M1X or whatever. We already know this chip isn’t going to go as is into the 16 inch MacBook Pro, the iMac Pro or the Mac Pro. I’d like to see what comes in those boxes.

aunetx 6y ago
I may be wrong, but the ecosystem does not really change here right? I mean, memory management should be roughly the same between x86_64 and arm regarding the amount of ram used, so I guess 16gb of ram under old macbooks is the same as 16gb under the new ones
- sudhirj 6y ago
  All else being equal, yes, but the memory is faster, closer to the chip, has less wiring to go through, and because of vertical integration they can pass by reference instead of copying values internally on the hardware. The last one is big - because all the parts of the SoC trust each other and work together they can share memory withing having to copy data over the bus. That coupled with superfast SSDs means that comparisons aren't Apples to oranges, excuse the pun. 16GB of memory on-die shared by all the components of an SoC is not the same as 16GB made available to separate system components, each of which will attempt to jealously manage their own copy of all data.
  - kcartlidge 6y ago
    I'm not a hardware person, but I do software for a living. Your comment makes things much clearer. You're saying that the effective difference in having the shared memory is that you get more data passed by reference and not by value at the lower levels? If that's true, then you get extra throughput by only moving references around instead of shuffling whole blocks of data, and you also gain better resource usage by having the same chunks of allocated memory being shared rather than duplicated across components?

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gumby 6y ago

> memory on-die or in-package (not sure how it is configured). They call it 'Unified Memory' It’s in the package; RAM on the die is called “cache”. “Unified memory” has nothing to do with packaging. It’s the default for how computer memory has worked since, well, the 1950s: all the parts talk to the same pool of memory (and you can DMA data for any device). That’s why the term of art for, say, GPUs having their own memory, is called NUMA (“Non-Uniform Memory Access”): unified is the default.) * M1 is a remarkable chip and Apple doesn’t claim that UFA is some invention: they just used the technical term, just as they say their chips use doped silicon gates. It has become unusual these days and worth their mentioning, but it’s simply ignorance by the reporters that elevated it to seem like some brand name. * https://en.wikipedia.org/wiki/Non-uniform_memory_access https://en.wikipedia.org/wiki/Non-uniform_memory_access

Symmetry 6y ago
In a NUMA system all the memory is in the same address space even if it's faster for a core to talk to some places than other. Traditionally GPUs work in a completely different address space and doesn't use virtual memory. Yes you can DMA to it but if you DMA a pointer it will break on the other end.

herf 6y ago

Anandtech is reporting 62GB/sec memcpy, and the way-faster Geekbench results are the memory-bound ones (e.g., Gaussian blur is 4x faster!) So I think the speedups like these are largely due to memory architecture.

mikechen233 6y ago
It's not due to the on package or the united memory. M1 is using industry standard 128bits lpddr4. On package is still using regular dram chips. What seemingly is the advantage is the firestorm cpu has much wider pipeline and capable doing more load and store in-flight at the time. Also the cache is also able to provide low latency and the bandwidth numbers. Intel or amd is able to achieve similar performance in memory bound workloads if they designed the logic on cpu for that workload.

pwinnski 6y ago

Putting the memory into the SoC seems to be a lot of how they're getting this amazing performance: the memory bus is now twice as wide as anything else. But yes, it means that Apple is going to have to either really start jamming more and more into there, or develop a two-tiered approach to memory where slower "external" RAM can supplement the faster "internal" RAM.

wmf 6y ago
The memory bus is now the same width as every other laptop.

Eric_WVGG 6y ago

I'm afraid I lost the source, but this morning I was reading about some fairly in-depth Xcode benchmarks, the dev was saying that there was almost no hit in performance when it hit swap, and speculated that Apple might be getting ready to move past the concept of RAM altogether in a few years. Sounds a little bonkers to me, but the bus to the SSD is no joke

mikechen233 6y ago
Next gen consoles and Nvidia rtx io is kind of doing that with graphics textures. Textures are memory mapped but stored in nvme storage. When GPU reads a texture, it first looks in the ram, if not found in the ram, the controller talks to nvme controllers to load from storage. If you think about it, gen4 pce nvme can reach 5GB/s doing 16k ramdom reads. The bandwidth is getting close to ddr2/3 territory. And new storage tech like 3dxpoint will have ram like access latency to improve small io perf. You will always still need ram, but you can be more efficient at how to use the ram.
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Eric_WVGG 6y ago
here's the source of that comment: https://twitter.com/panzer/status/1328708737482121217?s=21 https://twitter.com/panzer/status/1328708737482121217?s=21 I'm still a little unclear on whether he means "concept of RAM" in a marketing sense, discrete RAM, or a model closer to L3 cache. regardless, pure speculation

Symmetry 6y ago

It's certainly in package rather than on the same chip. The process required to make DDR is different from what you use to make the core's logic. The DRAM chips might be literally stack on top of the CPU chip, though. Apple does things that way in the iPhone IIRC.

jjtheblunt 6y ago

Maybe ARM binaries are smaller than x86_64? ARM has some sophistication in its ISA, THUMB mode instructions for example, that might be in play here.

duskwuff 6y ago
Thumb isn't a factor. The Thumb encoding is only used for 32-bit ARM instructions; 64-bit instructions use a fixed-width 32-bit encoding.