Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

GigaByte CXL memory expansion card with up to 512GB DRAM

gigabyte.com

Post reply on HN
Print view View original

21–30 of 67 posts

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

#21

Post by Dylan16807 »

GordonS wrote: post #17
Twirrim wrote: post #7

CXL is going to be really interesting. On the positive side, you can scale out memory quite a lot, fill up PCI slots, even have memory external to your chassis. Memory tiering has a lot of potential. On the negative side, you've got latency costs to swallow up. You don't get distance from CPU for free (there's a reason the memory on your motherboard is as close as practical to the CPU) https://www.nextplatform.com/20…

Huh, 200ns is less than I imagined; even if it is still almost 100x slower than regular RAM, it's still around 100x faster than NVMe storage.

Regular RAM is 50-100ns.

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

#23

Post by Dylan16807 »

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.

RAM controllers are expensive enough that it's rarely worth pairing them with old RAM lying around.

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

#24

Post by aidenn0 »

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.

(S)ATA or PCI to DRAM adapters were widely available until NAND became cheaper per bit than DRAM, at which point the use for it kind of went away.

IIRC Intel even made a DRAM card that was drum-memory compatible.

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

#25

Post by christkv »

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.

Check out Strix Halo 395+ it’s got 8 memory channels up to 128 GB and 16 cores

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

#26

Post by reilly3000 »

cjensen wrote: post #3
roscas wrote: post #2

That is amazing. Most consumer boards will only have 32 or 64. To have 512 is great!

Both of the supported motherboards support installation of 2TB of DRAM.

Presumably this is about adding more memory channels via pcie lanes. I’m very curious to know what kind of bandwidth one could expect with such a setup, as that is the primary bottleneck for inference speed.

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

#27

Post by Dylan16807 »

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.

DDR1 and DDR2 were clocked 20x and 10x slower than DDR5. The CPU cores we have now are faster but not that much faster, and with the typical user having 8 or fewer performance cores 128 bits of memory width has stayed a good balance.

If you need a lot of memory bandwidth, workstation boards have DDR5 at 256-512 bits wide. Apple Silicon supports that range on Pro and Max, and Ultra is 1024.

(I'm using bits instead of channels because channels/subchannels can be 16 or 32 or 64 bits wide.)

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

#28

Post by Dylan16807 »

christkv wrote: post #25
kvemkon wrote: post #16

Earlier quoted context omitted.

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.

Check out Strix Halo 395+ it’s got 8 memory channels up to 128 GB and 16 cores

That's a true but misleading number. It's the equivalent of "quad channel" in normal terms.

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

#30

Post by wmf »

JonChesterfield wrote: post #29

I don't get it. The point of (ddrN) memory is latency. If its on the far side of pcie latency is much worse than the system memory. In what sense is this better than ssd on the far side of pcie?

It's only ~2x worse latency than main memory but 100x lower than SSD.
Post reply on HN