8 ms·

"What is quite astonishing, is just how close Apple’s A11 and A12 are to current desktop CPUs. I haven’t had the opportunity to run things in a more comparable

"What is quite astonishing, is just how close Apple’s A11 and A12 are to current desktop CPUs. I haven’t had the opportunity to run things in a more comparable manner, but taking our server editor, Johan De Gelas’ recent figures from earlier this summer, we see that the A12 outperforms a Skylake CPU." How do they do it?

tinus_hn 8y ago
1. It probably helps if you don’t have to accommodate 30 years of legacy. 2. The mobile phone industry is fiercely competitive while the PC industry has Intel and their near-monopoly.
- hesdeadjim 8y ago
  Legacy isn’t a good explanation because the instruction decoder that turns x86 instructions into microcode is basically a fixed cost and makes up a tiny portion of the silicon. Clearly there is room for innovation in the x86 sphere as well because the AMD Zen architecture was created brand new from scratch and has become very competitive. The more likely explanation is that there is an exponential difficulty curve in CPU optimization and performance that Apple and their admittedly talented engineers are climbing very quickly. When an Ax chip hits true desktop performance sooner than later, the limit of physics is going to slow down Apple just like it has Intel and AMD. There isn’t any magic they are going to be able to do that suddenly gives them a 2x IPC gain or huge frequency advantage.
  - umanwizard 8y ago
    Well my Intel chip needs a fan and my iPhone doesn’t. So it’s not an apples-to-apples comparison (no pun intended, please nobody reply with “I see what you did there”). The fact that someone can come up with a chip of similar performance to Intel’s isn’t that amazing. The fact that they can do so without needing a fan is.
    - oliveshell 8y ago
      I agree— though it’s perhaps worth mentioning that a fan on the phones was used for the SPEC2006 benchmarks: > The performance measurement was run in a synthetic environment (read: bench fan cooling the phones) where we assured thermals wouldn’t be an issue for the 1-2 hours it takes to complete a full suite run. Still darn impressive, as in the real world you won’t be doing anything with your phone that maxes out the SoC for 2 hours straight.
    - hesdeadjim 8y ago
      The performance comparisons are not remotely apples to apples to begin with. All that's been established is that an Ax chip is entering the realm of desktop performance. Under all the workloads you'd benchmark a regular desktop chip on (FPU, AVX, etc etc) the Ax chips are still going to be far behind at the TDP and frequency they run at. If you could pump up the TDP and frequency of the Ax chips to actual desktop class and throw a heatsink on so you don't get thermally throttled, I am sure Apple's chips would be competitive. It's an inevitability that we'll see a desktop-class Ax powered Macbook at some point soon-ish. When that happens we can start making legitimate comparisons.
  - tinus_hn 8y ago
    Due to all that legacy the instruction decoder has a lot less opportunity for optimizations. There may be a physical limit to the size of transistors but the limit of computing performance is not ‘what Intel is doing’. There’s more to performance than instructions per second or clock frequencies. In fact these don’t lead to the same performance at all as ARM is RISC and x64 is CISC.
    - z0d 8y ago
      That RISC and CISC, nobody mentioned until yours. Why are people only caring about Perf/watt or the SoC beating out the ST perf of the Skylake uarch. RISC based processor with that level of cache is always having an advantage due to the Load and Store at register level (esp in this A12 case of having HUGE L$) vs the CISC's more transistor level perf + DRAM to exec instructions, causing higher TDP requirements PLUS the multi instruction execution parallelism capabilities. And entirely different code of AArch64 and x86_64. Add the GPU and Direct X, and Encode/Decode functionality I know this is not the subject, the ARM processors simply cannot keep up. The author did also mention the limitations of the comparison also as mentioned above the Skylake Xeon is capable of running Hex channel ECC Memory with huge capacity that alone will outpace everything on ARM it's not a fair share of comparison at all. GB is an OS level optimized bench. There's simply no comparison point that exists. Like I'd say to the author do a 4D render bench like Cinebench then we talk on this. He should at-least have mentioned the uarch part. Also on a side note, Apple underselling the chips ? That's really first, since Apple always over promises. Their latest meltdown on the MacBooks with low quality/specced VRM throttling the CFL machines is a joke.
  - astrange 8y ago
    That x86 support isn't free. Intel's SIMD implementations and new instructions only ever seem to target the high end; I don't think you could use AVX512 at low power. They also guarantee various things about memory ordering that ARM doesn't, and of course the page table, 16-bit boot modes, and everything are super complicated.
- ChuckMcM 8y ago
  I would expect there is some legacy aspect to it, although Intel building the Itanium (no legacy restrictions) just made a box that used more watts per instruction than their 32 bit line and wasn't that much better off. That said, things like the 'half carry' flag, segment pointers, and a large power hungry FPU don't help the Intel story. I expect the primary difference one will find is that Intel has more "large" cores in their chips (full fledged cores) and the comparable instructions have some "gotchas" (like the flag mention) which make them harder to retire early in the pipeline. Toshiba made a funny comment at one of the Microprocessor forums that for their microprocessors, if you only compare the instructions that both they and Intel implement, the Toshiba processor is better in every way. What is clearly true though is that compatibility aside, ARM chips are becoming serious contenders in the desktop/laptop space sooner than I expected them too.
oflannabhra 8y ago
Apple gets a lot of flack for the high margins on their products, but those high margins allow them to design and create high-cost SoCs. They also essentially have a business guarantee that all of the chips they fabricate will get purchased, at a know price and ROI. So, on top of the vertical integration of software/hardware advantage, they have diminished risk.
- ianai 8y ago
  They’re also optimizing for UI/UX by emphasizing single more performance. That’s what affects how fast and responsive the interface is to user input.
aquadrop 8y ago
I'm pretty skeptical of this. 3 W mobile CPU outperforms 165 W desktop CPU? If it was the case, they would have those things in macbooks already, and would boast tens of hours from one charge... If you go to the article that is mentioned in "recent figures", they tested single-core performance. So it was single core of a 28-core CPU (with boost though). It's still impressive, but not unbelievable.
- jonknee 8y ago
  The reason they don't have them in laptops is not because of performance, it's because they don't have an OS. A laptop that only runs iOS is called an iPad and it doesn't have the software I want to run.
  - aquadrop 8y ago
    My point was that if they had this abysmal advantage now, it means they would see it coming several years prior and would work on OS and anything else it needed. But it's not the point, main point is that I think statement that current A12 is close (to whatever reasonable %) to top desktop chips is simply not true. I didn't see any concrete evidence of it, and everyone just seem to like this idea, that's why it was talked much lately. I'm all for great advantages and all that, but I still must use common sense, 3-4W vs 150+ W - that's too much.
    - pertymcpert 8y ago
      People aren't comparing 3W mobile chips to 150W desktop CPUs. They're comparing like for like in terms of perf/watt. Skylake isn't a particular SKU, it's a micoarchitecture generation, from which Intel can scale the design from low power 10W parts to power hungry server chips.
      - aquadrop 8y ago
        Article reference specific CPU - Xeon 8176. It has 165W TDP.
    - 8y ago
JustSomeNobody 8y ago
The question should be for how long? Can it outperform a Skylake for 10 seconds? 30 seconds? 1 minute? 15 minutes? A burst for a few seconds is ok on a phone, but not on a server or workstation.
- pertymcpert 8y ago
  That's not really the question, because turbo boost exists on servers and workstations too. Intel chips will clock to 4.5GHz for a short while before throttling down to their base frequency once the thermal ceiling is hit.
- endorphone 8y ago
  But that isn't really the question rather than the answer -- in other profiles the chip could have significantly better heat dissipation solutions and would have dramatically more headroom.
baybal2 8y ago
Huuuiuuge caches, and optimisations for using them as efficiently as possible: probably async prefetch, possibly a semblance of maskable cache, very likely reordering for cache missing ops. Here, the prehistoric nature of x86 actually drags it down because of poor predictability
- astrange 8y ago
  x86-64 is decently predictable, probably the same as armv8. i386 wouldn't be because it has to spill to memory so much you can barely manage to rename those registers.
kbenson 8y ago
After looking at this closer, what they are comparing is single threaded performance of the Skylake Xeon 8176. At 28 cores and 56 threads, that watts per thread or core value starts to look somewhat comparable, given Apple's low core count (compared to that desktop CPU) and that they might not run the Vortex (2x) and Tempest (4x) cores at the same time(?). So, I think it's both a matter of comparing Apples to Oranges (ugh, I would use a less confusing analogy if one came to mind) in that the types and usage and number of cores are different, and also just fairly impressive that they can get that much single threaded performance out of the chip.
- frou_dh 8y ago
  IIRC one of the changes from the A10 to the A11 was that the different sized cores started being able to run simultaneously. Apparently the smaller Tempest core from the A12 is being used as the main core in the new Apple Watch. Talk about, uh, synergy.
  - wintercharm 8y ago
    Yeah. The S4 Apple watch SoC is actually using Two Tempest (LITTLE) cores. Pretty awesome, if you think about It. That little watch is more powerful than it appears.
- jfb 8y ago
  The craziest thing is how close they get at 3W. That's the part that's staggering. What could Apple do with, say, laptop thermals? Desktop thermals? The mind creeps closer to boggling.
  - FireBeyond 8y ago
    It's not that staggering. Use the above example. It's comparable to one thread of the 56 thread Xeon 8176. That server CPU has a TDP of 165W. That's 2.95W per thread. So pretty much entirely on par with Apple.
    - 8y ago

tinus_hn 8y ago

1. It probably helps if you don’t have to accommodate 30 years of legacy. 2. The mobile phone industry is fiercely competitive while the PC industry has Intel and their near-monopoly.

hesdeadjim 8y ago
Legacy isn’t a good explanation because the instruction decoder that turns x86 instructions into microcode is basically a fixed cost and makes up a tiny portion of the silicon. Clearly there is room for innovation in the x86 sphere as well because the AMD Zen architecture was created brand new from scratch and has become very competitive. The more likely explanation is that there is an exponential difficulty curve in CPU optimization and performance that Apple and their admittedly talented engineers are climbing very quickly. When an Ax chip hits true desktop performance sooner than later, the limit of physics is going to slow down Apple just like it has Intel and AMD. There isn’t any magic they are going to be able to do that suddenly gives them a 2x IPC gain or huge frequency advantage.
- umanwizard 8y ago
  Well my Intel chip needs a fan and my iPhone doesn’t. So it’s not an apples-to-apples comparison (no pun intended, please nobody reply with “I see what you did there”). The fact that someone can come up with a chip of similar performance to Intel’s isn’t that amazing. The fact that they can do so without needing a fan is.
  - oliveshell 8y ago
    I agree— though it’s perhaps worth mentioning that a fan on the phones was used for the SPEC2006 benchmarks: > The performance measurement was run in a synthetic environment (read: bench fan cooling the phones) where we assured thermals wouldn’t be an issue for the 1-2 hours it takes to complete a full suite run. Still darn impressive, as in the real world you won’t be doing anything with your phone that maxes out the SoC for 2 hours straight.
  - hesdeadjim 8y ago
    The performance comparisons are not remotely apples to apples to begin with. All that's been established is that an Ax chip is entering the realm of desktop performance. Under all the workloads you'd benchmark a regular desktop chip on (FPU, AVX, etc etc) the Ax chips are still going to be far behind at the TDP and frequency they run at. If you could pump up the TDP and frequency of the Ax chips to actual desktop class and throw a heatsink on so you don't get thermally throttled, I am sure Apple's chips would be competitive. It's an inevitability that we'll see a desktop-class Ax powered Macbook at some point soon-ish. When that happens we can start making legitimate comparisons.
- tinus_hn 8y ago
  Due to all that legacy the instruction decoder has a lot less opportunity for optimizations. There may be a physical limit to the size of transistors but the limit of computing performance is not ‘what Intel is doing’. There’s more to performance than instructions per second or clock frequencies. In fact these don’t lead to the same performance at all as ARM is RISC and x64 is CISC.
  - z0d 8y ago
    That RISC and CISC, nobody mentioned until yours. Why are people only caring about Perf/watt or the SoC beating out the ST perf of the Skylake uarch. RISC based processor with that level of cache is always having an advantage due to the Load and Store at register level (esp in this A12 case of having HUGE L$) vs the CISC's more transistor level perf + DRAM to exec instructions, causing higher TDP requirements PLUS the multi instruction execution parallelism capabilities. And entirely different code of AArch64 and x86_64. Add the GPU and Direct X, and Encode/Decode functionality I know this is not the subject, the ARM processors simply cannot keep up. The author did also mention the limitations of the comparison also as mentioned above the Skylake Xeon is capable of running Hex channel ECC Memory with huge capacity that alone will outpace everything on ARM it's not a fair share of comparison at all. GB is an OS level optimized bench. There's simply no comparison point that exists. Like I'd say to the author do a 4D render bench like Cinebench then we talk on this. He should at-least have mentioned the uarch part. Also on a side note, Apple underselling the chips ? That's really first, since Apple always over promises. Their latest meltdown on the MacBooks with low quality/specced VRM throttling the CFL machines is a joke.
- astrange 8y ago
  That x86 support isn't free. Intel's SIMD implementations and new instructions only ever seem to target the high end; I don't think you could use AVX512 at low power. They also guarantee various things about memory ordering that ARM doesn't, and of course the page table, 16-bit boot modes, and everything are super complicated.
ChuckMcM 8y ago
I would expect there is some legacy aspect to it, although Intel building the Itanium (no legacy restrictions) just made a box that used more watts per instruction than their 32 bit line and wasn't that much better off. That said, things like the 'half carry' flag, segment pointers, and a large power hungry FPU don't help the Intel story. I expect the primary difference one will find is that Intel has more "large" cores in their chips (full fledged cores) and the comparable instructions have some "gotchas" (like the flag mention) which make them harder to retire early in the pipeline. Toshiba made a funny comment at one of the Microprocessor forums that for their microprocessors, if you only compare the instructions that both they and Intel implement, the Toshiba processor is better in every way. What is clearly true though is that compatibility aside, ARM chips are becoming serious contenders in the desktop/laptop space sooner than I expected them too.

oflannabhra 8y ago

Apple gets a lot of flack for the high margins on their products, but those high margins allow them to design and create high-cost SoCs. They also essentially have a business guarantee that all of the chips they fabricate will get purchased, at a know price and ROI. So, on top of the vertical integration of software/hardware advantage, they have diminished risk.

ianai 8y ago
They’re also optimizing for UI/UX by emphasizing single more performance. That’s what affects how fast and responsive the interface is to user input.

aquadrop 8y ago

I'm pretty skeptical of this. 3 W mobile CPU outperforms 165 W desktop CPU? If it was the case, they would have those things in macbooks already, and would boast tens of hours from one charge... If you go to the article that is mentioned in "recent figures", they tested single-core performance. So it was single core of a 28-core CPU (with boost though). It's still impressive, but not unbelievable.

jonknee 8y ago
The reason they don't have them in laptops is not because of performance, it's because they don't have an OS. A laptop that only runs iOS is called an iPad and it doesn't have the software I want to run.
- aquadrop 8y ago
  My point was that if they had this abysmal advantage now, it means they would see it coming several years prior and would work on OS and anything else it needed. But it's not the point, main point is that I think statement that current A12 is close (to whatever reasonable %) to top desktop chips is simply not true. I didn't see any concrete evidence of it, and everyone just seem to like this idea, that's why it was talked much lately. I'm all for great advantages and all that, but I still must use common sense, 3-4W vs 150+ W - that's too much.
  - pertymcpert 8y ago
    People aren't comparing 3W mobile chips to 150W desktop CPUs. They're comparing like for like in terms of perf/watt. Skylake isn't a particular SKU, it's a micoarchitecture generation, from which Intel can scale the design from low power 10W parts to power hungry server chips.
    - aquadrop 8y ago
      Article reference specific CPU - Xeon 8176. It has 165W TDP.
  - 8y ago

JustSomeNobody 8y ago

The question should be for how long? Can it outperform a Skylake for 10 seconds? 30 seconds? 1 minute? 15 minutes? A burst for a few seconds is ok on a phone, but not on a server or workstation.

pertymcpert 8y ago
That's not really the question, because turbo boost exists on servers and workstations too. Intel chips will clock to 4.5GHz for a short while before throttling down to their base frequency once the thermal ceiling is hit.
endorphone 8y ago
But that isn't really the question rather than the answer -- in other profiles the chip could have significantly better heat dissipation solutions and would have dramatically more headroom.

baybal2 8y ago

Huuuiuuge caches, and optimisations for using them as efficiently as possible: probably async prefetch, possibly a semblance of maskable cache, very likely reordering for cache missing ops. Here, the prehistoric nature of x86 actually drags it down because of poor predictability

astrange 8y ago
x86-64 is decently predictable, probably the same as armv8. i386 wouldn't be because it has to spill to memory so much you can barely manage to rename those registers.

kbenson 8y ago

After looking at this closer, what they are comparing is single threaded performance of the Skylake Xeon 8176. At 28 cores and 56 threads, that watts per thread or core value starts to look somewhat comparable, given Apple's low core count (compared to that desktop CPU) and that they might not run the Vortex (2x) and Tempest (4x) cores at the same time(?). So, I think it's both a matter of comparing Apples to Oranges (ugh, I would use a less confusing analogy if one came to mind) in that the types and usage and number of cores are different, and also just fairly impressive that they can get that much single threaded performance out of the chip.

frou_dh 8y ago
IIRC one of the changes from the A10 to the A11 was that the different sized cores started being able to run simultaneously. Apparently the smaller Tempest core from the A12 is being used as the main core in the new Apple Watch. Talk about, uh, synergy.
- wintercharm 8y ago
  Yeah. The S4 Apple watch SoC is actually using Two Tempest (LITTLE) cores. Pretty awesome, if you think about It. That little watch is more powerful than it appears.
jfb 8y ago
The craziest thing is how close they get at 3W. That's the part that's staggering. What could Apple do with, say, laptop thermals? Desktop thermals? The mind creeps closer to boggling.
- FireBeyond 8y ago
  It's not that staggering. Use the above example. It's comparable to one thread of the 56 thread Xeon 8176. That server CPU has a TDP of 165W. That's 2.95W per thread. So pretty much entirely on par with Apple.
  - 8y ago