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> In what universe is that normal? In a universe where you want high-performance energy efficient RAM. Premium ultracompact laptops have long moved to LPDDR wh
by ribit 5y ago
> In what universe is that normal?
In a universe where you want high-performance energy efficient RAM. Premium ultracompact laptops have long moved to LPDDR which is both faster and consumes significantly less energy than regular modular DDR. And LPDDR does not come in DIMMs. And then you have Apple who are using custom package technology with custom RAM chips to cut down RAM power consumption to under one watt active, delivering close to 20 hours battery. You simply can’t have this with socketed RAM. Modularity is not a free lunch, as much as some people like to pretend.
- nspattak 5y agoCan you please point us to some technical report or something where they document the energy saving of moving from dimm slots to soldered ram/ssd ?
- ribit 5y agoUnfortunately, I am not aware of any document like that. There are some papers comparing everything efficiency of different types of RAM, and there is of course indirect evidence of premium notebooks having significantly improved the battery life after moving to LPDDR.
- formerly_proven 5y agoLPDDR does many, many things to reduce power consumption (the current version even does DVFS, which I think is a first for main memory; graphics cards have been doing interface DFS for a long time, but a high end graphics card will burn around 30-70 W in the memory chips, and uses extremely high speed PHYs running at around 20 GBit/s per pin in the current generation). The only thing that really changes between DIMM and soldered on is a somewhat increased trace length. That accounts only for a very small increase in power.
- foldr 5y ago> That accounts only for a very small increase in power. What are you basing this statement on?
- formerly_proven 5y agoPHY is only part of the DRAM chip, and trace length is only a part of what determines energy per bit, so increasing trace length by x % wouldn't increase overall power by x %, but a fraction of that. Thinking about it, there is a bigger problem than just energy/bit scaling; since LPDDR switches dynamically between high-speed and lower speed modes, the high speed mode is likely not used a lot. However, the low speed modes rely on being able to turn the termination off, which saves significant amounts of power. A socket may make that difficult to achieve, and if you have to run with ODT in the, I'm assuming, mostly-used low power mode, you might end up with a significant increase in power.
- foldr 5y agoOf course there are multiple factors at play, but that observation doesn’t justify the conclusion that any particular factor makes only a ‘very small l’ contribution. Do you have even a back-of-an-envelope calculation to support this claim? The knock-on effects of increased trace length can be quite complex.
- franga2000 5y agoI don't think you'll find any. The way I understand it, the savings come from the new LP variant of DDR chips and nobody ever bothered to put them on DIMMs. And even if the DIMM design (it's more than just a slot) doesn't make sense anymore, we could easily make a new "dumb" memory slot standard that would allow us to swap out the chips directly - like we have for CPUs.
- foldr 5y ago> we could easily make a new "dumb" memory slot standard that would allow us to swap out the chips directly - like we have for CPUs. You could, but it would take up a lot of space, given the higher pin count, and would most likely increase power consumption.
- ribit 5y agoBy the way, check out reviews of the Framework Laptop for a first-hand illustration of this effect. They seem to be getting 40-50% lower battery runtimes than laptops with comparable specs. That's example the problem — of you design for modularity, you have to leave some optimizations on the table.
- nrp 5y agoThe battery impact for us at this point is likely more a factor of additional firmware and driver tuning that we need to do. We've tested to 10-11 hours in MobileMark 2018, but have actually seen video playback runtime (which should be a lighter load) drop below that due to some audio driver issues that we're working through. There is certainly some impact to using DDR4 instead of LPDDR4, but we believe it is still the better choice for most consumers by allowing for greater product longevity at lower cost.
- collinmanderson 5y agoHow about standby time?
- formerly_proven 5y agoDoubtful, the Framework laptop is pretty much like any other USB-C-based laptop, except that it reserves some space inside the chassis so that the adapter dongles are flush with the case.
- michaelmrose 5y agoThat doesn't in any way tease out the effects of sockets it seems impossible that that doubles power usage.
- andresgottlieb 5y agoWhy is it that you can't have this with socketed RAM? Is there a physical limitation?
- Aeolun 5y agoI imagine you may have some difficulty getting the pins to make contact if they’re too small.
- franga2000 5y agoModern CPUs are an order of magnitude more complex and usually built on a smaller process, yet we have no trouble putting them on intermediary PCBs to spread out contacts and allow larger pins. I see no reason we couldn't make LGA sockets for DRAM chips in the same way.
- ribit 5y agoThe beauty and success of DIMM modules is that they are a simple slide-in to install technology. It's easy to operate, cheap, robust, and it is very space efficient. Imagine RAM modules in an LGA socket instead... how much space would it require? How robust would it be? What will be the price? I am quite sure all of these issues can be solved, but is it worth it? Let's be honest, users who are interested in having upgradeable RAM in their ultraportable laptop are such a small minority that the practical interest in developing modular low-powered RAM is close to zero.
- formerly_proven 5y agoThe practical interest might be close to zero because in the past memory upgrades a number of years down the road were one of the most common upgrades and added tremendous value and another few years of life. Similarly many older laptops got a second life by being upgraded to SSDs. Accidents like that, which prevent sales of new units, can't happen if storage and memory are soldered on. I don't think this is the driver of these decisions per se, but it is undeniably a bonus for the manufacturer; non-upgradable devices become obsolete faster, necessitating new replacements.
- michalf6 5y agoI would really prefer that a laptop was just a tiny bit thicker to fit a 100WH battery to compensate for that. My T480 gets 12-16 hours with normal use, I imagine it could easily hit 20 with current processors.
- ddalex 5y ago> a 100WH battery a hand grenade typically releases 250kJ, or about 70Wh you're asking for the equivalent of 1.5 grenades in your lap :)
- chrismorgan 5y agoAirlines tend to cap lithium-ion batteries at 100Wh, so it’s quite common for laptops and power banks to go to or just shy of that. https://www.apple.com/newsroom/2019/11/apple-introduces-16-inch-macbook-pro-the-worlds-best-pro-notebook/ https://www.apple.com/newsroom/2019/11/apple-introduces-16-i... speaks of a 100Wh battery. My latest laptop has about a 90Wh battery. Hopefully your laptop and hand grenade have radically different power discharge profiles.
- ddalex 5y ago> Hopefully your laptop and hand grenade have radically different power discharge profiles Li battery fires are not unheard of, unfortunately, so the profiles may start to resemble sometimes.
- littlestymaar 5y agoLithium batteries burn, quite quickly but it still takes a few seconds, that can be pretty dangerous indeed but that's several orders of magnitude slower than a grenade.
- grenoire 5y agoThe hand grenade is arguably better at releasing that energy at an instant.
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- franga2000 5y agoSo just...put LPDDR on a DIMM? Or some other kind of removable slot?? I see no technical reason you couldn't. Or, instead of soldering chips, make little LGA slots for the individual chips. I can't imagine the tiny added resistance from an extra millimeter of wire and pin surface contact would impact much of anything and even if it does, I'd rather take that than have no options when the next Windows update makes my machine a paperweight (obviously exaggerating, but it's getting there).
- pclmulqdq 5y agoThe reason is signal integrity. Running a high speed signal (never mind a bus of 64+ of them) through a connector is hard and takes a lot of power because the connector can seriously degrade the signals. LPDDR can be low power because it doesn't have a "memory stick" abstraction, just memory chips and controllers. It's not the resistance that kills the signal, it's the inductance and the impedance mismatching.
- jackcviers3 5y ago1 watt vs 2 Watts. Stop shilling.
- vbernat 5y agoFor something running at 5-6W while idle, this is not a small difference.
- bserge 5y agoLPDDR3 DIMMs exist. I assume everyone is talking about LPDDR4, which seems to use 0.1V less. But the majority of people couldn't give a toss about how much of their laptop ends up in a landfill. They're using paper/glass straws, you see. Perhaps electronics landfills should be local again.
- pclmulqdq 5y agoI think you're referring to DDR3L DIMMs, which are just a down-volted version of DDR3. LPDDR has never had DIMMs because of signal integrity issues. They take power to resolve.
- tomxor 5y ago> In a universe where you want high-performance energy efficient RAM [.....] You simply can’t have this with socketed RAM. You make it sound like a prerequisite. I'm pretty sure the reason LPDDR is Low Power is not due to (currently) being unavailable in socketed modules - that would seem to be a side-effect of the original target market (smart phones). They are just some BGA packages, I see no reason they couldn't be soldered onto a board with a socket. If you scan through the features that make LPDDR LP, they have nothing to do with sockets, or anything affecting sockets: lower operating voltage, more power states, partial refreshing etc: https://en.wikipedia.org/wiki/LPDDR https://en.wikipedia.org/wiki/LPDDR
- baybal2 5y agoYes, as I wrote somewhere below, LPDDR4 signal is actually more robust than DDR4 signal, and LPDDR4 controllers have more features to fix degraded signals. DDR5 has more roots in the LPDDR4 than in the regular DDR4.
- ribit 5y agoLPDDR is low power because it is a more sophisticated device with more complex protocol compared to regular DDR, because it has a higher pinout allowing it to have a more efficient electrical connection and because the computer manufacturer can optimize the connection with specific chips in mind instead of having to support a wide range of devices. I think the number of pins is a practical limitation. Current DDR DIMMs use 260-280 pins if I remember correctly, while an average LPDDR4X BGA package is 400 balls or higher. Apple uses chips with 877 balls. It is definitely possible to design modular RAM with high-pinout, but would it be economically feasible?
- rthomas6 5y agoIt is if it's a standard that everyone decides to support...
- ribit 5y agoThat's the thing, who is everyone? Such technology would only be relevant to premium-level ultraportable notebooks. Desktops, gaming laptops as well as budget laptops would stick with the cheaper and more ubiquitous DDR. Smartphones and tables will continue to solder RAM on due to space constraints. Apple (who is the driving force in this market segment) won't be interested since they are going fully custom and I doubt that an LGA socket will work with their on-package custom-build wide RAM interfaces. So in the end we are left with things like Dell XPS 13, MS Surface and few others. These are all popular and impactful brands, but they are just a drop in the bucket compared to the total PC sales. And I doubt that technology reserved to only selected premium laptops is going to be cheap.
- Const-me 5y agoRAM energy efficiency is not important because very small fraction of the energy consumed by other components. It only somewhat matters for power consumption in sleep mode when the RAM is the only component being powered, but at least on Windows that’s solvable with a fast SSD and hibernation.
- ribit 5y agoRAM energy efficiency is extremely important because it is a significant part of the baseline power consumption. Power-hungry components like CPU and GPU can be run in the lowest power state most of the time, so it really comes down to RAM and the display. If you have a 60Wh battery and want to get 15 hours battery life, you need to get your idle power consumption under 4 watts. So even 0.5 watt in baseline RAM consumption makes a huge difference.
- magicalhippo 5y agoI recall underclocking the RAM on my video card a few years ago when in desktop mode. Reduced the heat in the PC case by several degrees.
- Const-me 5y agoPerformance difference between system RAM and VRAM is an order of magnitude. Specifically, DDR4-3200 peaks at 25.6 GB/second per channel, modern high-end GPUs peak at 500-900 GB/second depending on the GPU model. VRAM consumes substantial power to deliver that performance. On many GPUs, VRAM chips are actively cooled. System RAM doesn’t even need passive heatsinks, uses too little electricity to care.
- formerly_proven 5y agoGPUs do use fairly fine-grained dynamic frequency scaling on their memory chips for precisely this reason: having a top-end GPU run at around 15-20 W under light loads simply wouldn't be possible otherwise.
- emilfihlman 5y ago>You simply can’t have this with socketed RAM. [Citation needed], there is no real electrical engineering reason why you couldn't.
- intricatedetail 5y agoThe problem is not that the chip is soldered, but that you can't buy it. Soldering BGA is not that difficult.
- carlhjerpe 5y agoI would have to leave it to a professional, I can barely solder connectors on my RC car power packs
- neycoda 5y agoI love the idea of needing to replace the laptop to upgrade RAM. /sarc
- lostlogin 5y agoI find this to be less of an issue than the noise it generates. If you maximise ram at purchase, the limitations of a laptop seem to be battery and storage more than anything else. A 8 year old MacBook is just fine for a lot of usage, except for the dead battery and limited storage. Having these easily repairable would make my life a lot easier - this laptop looks great.
- xondono 5y agoModularity is a great feature, but modularity is a mobility killer. Modular laptops, phones, etc.. will be always penalized in terms of either performance or battery life for a given size.
- jackcviers3 5y ago1 watt active is low. But so is 2 for dimm ddr3 [1]. They switched to make upgrading more difficult. "Typical Power Consumption of PC Components - Power Draw in Watts" https://www.buildcomputers.net/power-consumption-of-pc-components.html https://www.buildcomputers.net/power-consumption-of-pc-compo...
- eropple 5y agoYou've repeated this in a few places in this thread with this same sort of conspiratorial air, but when you are talking about south of 10W total consumption (sometimes south of 6W!), a watt is a very significant amount and has a very large impact on overall battery life.
- specialist 5y agoPlease forgive the hi-jack... FWIW, the book Design Rules: The Power of Modularity systematically explores the tradeoffs. https://www.amazon.com/Design-Rules-Vol-Power-Modularity/dp/0262024667 https://www.amazon.com/Design-Rules-Vol-Power-Modularity/dp/... Written by two economists, it's the only prescriptive definition of architecture that I've managed to find. Influenced me deeply.
- wolverine876 5y agoSo why are you holding back on us? :) What are the main trade-offs?
- specialist 5y agoHeh. Just what you'd guess. Interfaces allow separation of concerns, parallel dev efforts, competition. Integration allows optimization, at greater risk. Their core contribution is modeling the options with net present value (NPV) to remove the guess work. -- Tangentially... They also explain the dependency structure matrix (DSM), a tool for modeling and visualizing architectures. One big takeaway for me was their explanation of "complexity catastrophe". The crossover point when the cost of change exceeds the benefit. A metaphor superior to most interpretations of "technical debt", IMHO. So when you have a DSM, these kinds of problems pop out, can't be ignored.
- deleted 5y ago[deleted]
- howinteresting 5y agoThen make the CPU+RAM user-replaceable. Where there's a will there's a way. The problem is there's no will.
- goodpoint 5y ago> Modularity is not a free lunch Hold on. This is true for excessive modularity. Yet, most of the time, lack of modularity (e.g. bundling) creates lock-in reducing customer's choice and ultimately increasing prices. When PCs became standardized ( https://en.wikipedia.org/wiki/IBM_PC_compatible https://en.wikipedia.org/wiki/IBM_PC_compatible ) prices dropped incredibly.
- nrp 5y agoWe believe that socketing memory is a good tradeoff to enable greater longevity through memory upgrades, and also a more useful upgrade path by being able to keep your memory during certain mainboard upgrades. In the DDR5 timeframe, there is less of a power delta as well between DDR5 and LPDDR5.
- goodpoint 5y ago> In a universe where you want high-performance energy efficient RAM You are cherry-picking an example that fits only a specific category of laptops. Even so, CPU and RAM could be bundled together into a socketed cartridge that is easy to upgrade. The real reason is all about planned obsolescence and profit margins.