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by wtallis 8 days ago
> Framework already sells LPCAMM2 at 8533MT/s with full validation:

From your link:

> Framework Laptop 13 Pro (Intel® Core™ Ultra Series 3) supports one slot of LPCAMM2 memory up to 96GB at the native 7467 MT/s speed. It is compatible with LPCAMM2 modules with memory speed rated above 7467 MT/s, but the speed will be capped at 7467 MT/s because of the platform limitation.

The modules in question can only theoretically operate at 8533MT/s. Framework has yet to sell a system where the modules actually operate at more than 7467MT/s.

> It turns out Apple isn't getting 9600MT/s either. I assumed that soldering would be getting them at least what LPCAMM2 is rated for, but if you actually do the math, they're getting ~8500MT/s for their most expensive systems and ~7500MT/s for the others.

You're either doing the math wrong, or just plain looking at the wrong systems. Try looking at the M5 generation.

> CAMM modules use a compression fitting to attach the chips to the system board using approximately the same amount of space as the solder pads would for soldered chips. If you get to the point of having so many channels that the chips are in the way of the other chips then the soldered ones have the same problem.

Yes, that's a problem, and Apple has solved it by moving the DRAM on-package. Datacenter GPUs have also solved it that way by putting the DRAM on a silicon interposer to allow even wider bus widths. Soldering standard DRAM packages on the motherboard is not the limit of how memory can be soldered down.

> A single LPCAMM2 module is a 128-bit bus. Every system that uses it has at least that.

Yes, 128 bits at lower speeds. Did you forget that the whole point I'm making here is that the speeds are not the same?

> Nobody is really using a bus that wide with soldered memory either though, outside of the couple of Macs that start at ~$3500 and are getting the same speed Framework does with LPCAMM2.

The Mac Studio with the M3 Ultra is actually running the DRAM at a lower frequency than what Framework and other Intel-based systems could, but more than making up for it in bus width, to provide far more total memory bandwidth than any plausible LPCAMM2-based system that could be built today.

1 comments

> You're either doing the math wrong, or just plain looking at the wrong systems. Try looking at the M5 generation.

The M5 generation isn't "1.5 years old" and even those aren't all that speed. The M5 Max with the 32-core GPU is ~7200MT/s, while the one with the 40-core GPU is over $4000.

> Yes, that's a problem, and Apple has solved it by moving the DRAM on-package.

There is no "package" here. Apple's processors are soldered to the logic board, as are Intel's in laptops. The DRAM Apple uses is standard LPDDR5 from the normal OEMs. Have a look at the LPCAMM2 module. It has four standard DRAM chips on the top and a connector on the bottom. DDR5 channels are really 32-bits, so the 128-bit module has four channels, four chips. The module is barely any larger than the chips themselves. It's not saving significant space by soldering them, it's just an alternative means of attaching them to the system board in the same place.

> Yes, 128 bits at lower speeds.

At the same speeds Apple was shipping a few months ago. Apple being the first to ship LPDDR5-9600 when it was that recent doesn't imply that it needs to be soldered, it implies that they're a huge company that can pay for early access to the new thing whether it's soldered or not. 9600MT/s LPCAMM2 modules have already been announced -- it's not a technical problem, it's an "Apple and OpenAI are buying out the fastest DRAM right now" problem.

> The Mac Studio with the M3 Ultra is actually running the DRAM at a lower frequency than what Framework and other Intel-based systems could, but more than making up for it in bus width, to provide far more total memory bandwidth than any plausible LPCAMM2-based system that could be built today.

By this logic the thing to beat it is the 8S Xeon servers from almost a decade ago with 48 channels of DDR4-2666. Or existing 2S servers with 24 channels of DDR5-6400.

> The M5 Max with the 32-core GPU is ~7200MT/s,

Ok, so the problem is you doing the math wrong. Note that the MacBook Pro configuration you're talking about has a DRAM capacity of 36GB, compared to 48+ GB for the ones with all the cores enabled and the full memory bandwidth. That 32-core config isn't running the DRAM slower, it's running with a narrower bus and fewer DRAM chips: https://theapplewiki.com/wiki/MacBook_Pro_(16-inch,_M5_Max)

> There is no "package" here. Apple's processors are soldered to the logic board, as are Intel's in laptops.

Denying the difference between putting the RAM on-package vs on the motherboard doesn't make that difference stop being real.

> Apple being the first to ship LPDDR5-9600 when it was that recent doesn't imply that it needs to be soldered

Apple wasn't even close to being the first to ship LPDDR5-9600. Android phones using DRAM at that speed started shipping at the end of 2023, and moved on to 10700MT/s starting in 2024. The situation here is not anywhere close to being one of Apple paying a premium to get faster DRAM chips that other laptop manufacturers can afford. Rather, for most of the past several years, laptop manufacturers (especially on the x86 side) have been unable to buy DRAM chips with a rating slow enough to match what their processors are capable of running at. It's become quite common to see on a Thinkpad spec sheet that eg. the DRAM parts are rated for 7467MT/s but will only operate at 6400MT/s due to processor limitations, then the next year see that the DRAM parts are rated for 8533MT/s but run at 7467MT/s, and so on. LPDDR speed increases have been driven primarily by flagship smartphones, and even the leftover slower-binned parts are faster than what most laptops can handle.