Servethehome posted a few benchmark results with EPYC 9654 on 8 channels RAM vs. 12 channels RAM. (Scroll down to the graph "ASRock Rack GENOAD8UD 2T X550 Performance 8ch To 12ch Reference". This was measured on different mainboards, but the difference in RAM channel count should be the biggest influence.) There is not a lot of a performance drop in most of these benchmarks. However, EPYC 9654 has got 12 CCXs. I wonder if SKUs with 8 CCXs (EPYC 9274F is one of those) have any performance drop at all if going with 8 instead of 12 RAM channels.In my case, I choose to go with Epyc 9274F due to it's great base frequency [...]
Also one Micron RDIMM 2R DDR5 4800 memory module arrived(From one seller), 5 more on the way(From another), and today got a deal on eBay for 2 extra used modules for only 120$ for both of them, so instead of originally planned 6 I will go for 8 modules,
thus 8 channels.
Servethehome posted a few benchmark results with EPYC 9654 on 8 channels RAM vs. 12 channels RAM. (Scroll down to the graph "ASRock Rack GENOAD8UD 2T X550 Performance 8ch To 12ch Reference". This was measured on different mainboards, but the difference in RAM channel count should be the biggest influence.) There is not a lot of a performance drop in most of these benchmarks.
They mentioned that their test wasn't quite bandwidth bound, and mentioned they expect larger differences for more intensive tests.If we were running something almost purely memory bandwidth bound like STREAM Triad, we would of course have larger variances. There are some applications that are effectively not memory bandwidth sensitive after a minimum threshold is reached, and those applications performed well.
Whats quite interesting question. I think there are debates about it every Epyc/TR release of how amount of CCDs will balance with memory controller.I wonder if SKUs with 8 CCXs (EPYC 9274F is one of those) have any performance drop at all if going with 8 instead of 12 RAM channels.
Hah! You asked about a cooler, they responded about a mounting kit...I've asked em' on 24.03 about some love for our small and cute SP5 socket, and got this response on 28.03:
Response:Do you plan to manufacture/introduce a socket SP5 (LGA 6096) compatible cooler for AMD Epyc Genoa CPUs? [...] will SP5 socket get some love as well, before TR-7000 release?
[...] Unfortunately, no such mounting kit is currently planned.
According to the publicly available Overview of AMD EPYC™ 7003 Series Processors Microarchitecture, access to AMD's Milan memory population guide requires a login. However, there is for example a publicly available guide for memory population of Milan based Dell servers: Memory Population Rules for 3rd Generation AMD EPYC™ CPUs on PowerEdge ServersAs a legacy note, and a little off-topic: EPYC 7002 'Rome' performs terrible if the number of populated channels differs from 4 or 8, even in applications which are not quite memory bandwidth sensitive. EPYC 7003 'Milan' was improved in this regard and works pretty well with 2, 4, and 6 (but of course best with 8) populated channels. AMD published the order in which channels should be populated for optimum performance, but I don't have a bookmark.
Welcome to the Genoa family ! I got one more 9554 since my last post, so, 3 9554's and a 9654, all air cooled. You are the first with a water cooled Genoa !I almost finished building a 64-core Genoa computer too now. It is watercooled.
Running 64 SGS-LLR tasks at once...
... on dual EPYC 7452 (2x 32 Zen 2 cores/ 2x 180 W cTDP):
723 s average elapsed time, ~370 W at the wall (305 kPPD, ~820 PPD/W)
Cores are running at about 2.6 GHz.
... on EPYC 9554P (64 Zen 4 cores/ 360 W TDP):
408 s average elapsed time, ~420 W at the wall (540 kPPD, ~1,290 PPD/W)
Cores are running at about 3.3 GHz.
I.e., +77 % computer performance, +14 % higher power draw, +56 % power efficiency from 2P air-cooled Rome to 1P water-cooled Genoa in this vector arithmetic centric workload.
Concentrating this much power in a single socket unfortunately complicates cooling if you want to avoid extreme noise, and increases power draw of the cooling subsystem somewhat.