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GigaByte CXL memory expansion card with up to 512GB DRAM

gigabyte.com

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Re: GigaByte CXL memory expansion card with up to 512GB DRAM

#61

Post by justincormack »

kvemkon wrote: post #16
jonhohle wrote: post #14

Why did something like this take so long to exist? I’ve always wanted swap or tmpfs available on old RAM I have lying around.

I'd have rather a question why we had single (or already dual) core CPUs with dual-channel memory controller and now we have 16-core CPUs but still with only dual-channel RAM.

AMD EPYC has 12 channel, 24 on dual socket. AMD sell machines with 2 (consumer), 4 (threadripper), 6 (dense edge), 8 (threadripper pro) and 12 memory channels (EPYC high end). Next generation EPYC will have 16 channels. Roughly if you look at the AMD options, they give you 2 memory channels per 16 cores. CPUs tend to be somewhat limited in what bandwidth they can use, eg on Apple Silicon you cant actually consume all the memory bandwidth on the wider options just on the CPUs, its mainly useful for the GPU. DDR5 was double speed of DDR4, and speeds have been ramping up too, so there have been improvements there.

Re: GigaByte CXL memory expansion card with up to 512GB DRAM

#62

Post by numpad0 »

jonhohle wrote: post #14

Why did something like this take so long to exist? I’ve always wanted swap or tmpfs available on old RAM I have lying around.

Yeah. I can't count how many times I've seen descriptions of northbridge links smelling like the author knows it's PCIe under the hood. I've also seen someone explaining that it can't be done on most CPUs unless all cache systems are turned off because (IO?)MMU don't allow caching of MMIO addresses outside DRAM range.

The technical explanations for the fact that you (boolean)can't have extra DRAM controllers on PCIe is increasingly sounding like market segmentation reasons than purely technical ones. x86 is a memory mapped I/O platform. Why we can't just have RAM sticks on RAM addresses.

The reverse of this works btw. NVMe drives can use Host Memory Buffer to cache reads and writes on system RAM - the feature that jammed and caught fire on recently rumored bad ntfs.sys incident in Windows 11.

Re: GigaByte CXL memory expansion card with up to 512GB DRAM

#64

Post by bobmcnamara »

to11mtm wrote: post #41
bobmcnamara wrote: post #35

Earlier quoted context omitted.

Intel and AMD I'd reckon. Apple went wide with their busses.

Well, Each Channel needs a lot of pins. I don't think all 288/262 pins need to go to the CPU, but a large number of them do, I'd wager; The old LGA 1366 (Tri-Channel) and LGA 1151 (Dual Channel) are probably as close as we can get to a simple reference point [0]. Apple FBOW, based on a quick and sloppy count of a reballing jig [1], has something on the order of 2500-2700 balls on an M2 CPU. I think AMD's FP11 'socket…

Completely agree, and this is a bit of a ramble...

I think part of might be that Apple recognized that integrated GPUs require a lot of bulk memory bandwidth. I noticed this with their tablet derivative cores having memory bandwidth that tended to scale with screen size but Samsung and Qualcomm didn't bother for ages. And it sucked doing high speed vision systems on their chips because of it.

For years Intel had been slowly beefing up the L2/L3/L4.

M1Max is somewhere between Nvidia 1080 and 1080TI in bulk bandwidth. The lowest end M chips aren't competitive, but near everything above that overlaps even the current gen NVIDA 4050+ offerings

Re: GigaByte CXL memory expansion card with up to 512GB DRAM

#65

Post by to11mtm »

bobmcnamara wrote: post #64
to11mtm wrote: post #41

Earlier quoted context omitted.

Well, Each Channel needs a lot of pins. I don't think all 288/262 pins need to go to the CPU, but a large number of them do, I'd wager; The old LGA 1366 (Tri-Channel) and LGA 1151 (Dual Channel) are probably as close as we can get to a simple reference point [0]. Apple FBOW, based on a quick and sloppy count of a reballing jig [1], has something on the order of 2500-2700 balls on an M2 CPU. I think AMD's FP11 'socket…

Completely agree, and this is a bit of a ramble... I think part of might be that Apple recognized that integrated GPUs require a lot of bulk memory bandwidth. I noticed this with their tablet derivative cores having memory bandwidth that tended to scale with screen size but Samsung and Qualcomm didn't bother for ages. And it sucked doing high speed vision systems on their chips because of it. For years Intel had been…

Good ramble though :)

Yeah, Apple definitely realized that they should do something and for as much as I don't care for their ecosystem I think they were very smart in how they handled the need for memory bandwidth, e.x. having more 16 bit channels vs fewer 64 bit channels probably allows for better power management characteristics as far as being able to relocating data on 'sleep'/'wake' and thus being able to leave more of the ram powered off.

That plus the good UMA impl has left the rest of the industry 'not playing catchup' i.e.

- Intel failing to capitalize on the opportunity of a 'VRAM heavy' low end card to gain market share,

- AMD failing to bite the bullet and meaningfully try to fight Nvidia on memory/bandwidth margin...

- Nvidia just raking that margin in...

- By this point you'd think Qualcomm would just do an 'AI Accelerator' reference platform just to try....

- I'm guessing whatever efforts are happening in China, they are too busy trying to fill internal needs to bother boasting and tipping their hat; better to let outside companies continue to overspend on the current paradigm.

Re: GigaByte CXL memory expansion card with up to 512GB DRAM

#67

Post by jonbiggums22 »

gertrunde wrote: post #20
jonhohle wrote: post #14

Why did something like this take so long to exist? I’ve always wanted swap or tmpfs available on old RAM I have lying around.

Such things have existed for quite a long time... For example: https://en.wikipedia.org/wiki/I-RAM (Not a unique thing, merely the first one I found). And then there are the more exotic options, like the stuff that these folk used to make: https://en.wikipedia.org/wiki/Texas_Memory_Systems - iirc - Eve Online used the RamSan product line (apparently starting in 2005: https://www.eveonline.com/news/view/a-history-of-e…

Are these the same thing though? I have a fondness for novel hardware and the idea of using up old ram standards to create a fast ram disk is interesting to me. But the CXL card seems to require motherboard/platform support whereas these older ram drives just showed up as a disk.
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