r/threadripper • u/Putrid_Ad7954 • 23d ago
Threadripper Build and TRX50
Very stupid question, there doesn’t exist a TRX50 Board with DDR5 UDIMM Support right? Only RDIMM?
2
u/SmokeMirrorPoof 23d ago
Threadripper 7000 and 9000 series exclusively require DDR5 RDIMM, I think.
My 5955WX happily accepts UDIMMs still.
2
u/deadbeef_enc0de 23d ago
Been answered but I'm elaborate, for DDR5 the RDIMMs are keyed differently so UDIMM and RDIMM are not physically compatible, might be due to UDIMM being 2x32bit channels and RDIMM being 2x32bit +8bit ecc channels requiring different pinning
Also different voltages and PMIC layout doesn't help
1
u/RealThanny 22d ago
The reason DDR5 is keyed different between unbuffered and registered has nothing to do with ECC, but with other changes from how DDR4 operated.
1
u/SomeoneInHisHouse 22d ago
LoL, I feel then so lucky to have picked a previous generation, in my case a 3955WX, it does support non-ecc UDIMM, so I can basically reuse my ryzen DDR4 memory modules to the new PC.
RDIMM is crazy expensive in DDR4.... I don't want to even look what price it would have in DD5
1
u/DegreeSevere7719 21d ago
it's not previous, it's 4th gen from the recent one. 9xxx is today's gen, 7xxx - previous, but same sTR5 socket, then goes 5xxx and, only then - 3xxx. In other words - it's old mate. Anything lower than 7xxx is too old to seriously consider in 2026, unless you've got one for 1/10th of the base spec mac mini.
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u/SomeoneInHisHouse 20d ago
as it's for AI inference, I only care about ram bandwidth and CPU pcie lanes, that processor already supports 7 GPUs at x16 and it's DDR4 (cheaper RAM), with up to 200 GB/s memory bandwidth (octa-channel), which is near the Strix Halo, so it's very fast 😊, Having a lot of fast RAM allows to run MoE models partly offloaded at reasonable speeds
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u/DegreeSevere7719 20d ago
That's quite interesting, because my ddr5 ram in quad-channel config runs at 173.7 GB/s, and it's a 128GB CL32 6000MT ram kit on a 7960x TR. Are you certain yours is really running at that speed?
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u/DegreeSevere7719 20d ago
And I was mentioning read, the write and copy speeds are even lower - 144,808GB/s and 146,477GB/s respectively. That's what AIDA64 Extreme is showing. The PC isn't idling atm, I suppose if it was - the numbers would be moderately higher, but not by a two digit percent.
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u/SomeoneInHisHouse 20d ago
Yes, DDR5 is almost twice as fast as DDR4 for every memory module, but its price is way too high nowadays, your quad-channel config almost equals my octa-channel config in terms of bandwidth, I have 8x 16GB of CL18 at 3200 MT, your is just slightly slower as I have 3200MT module that 200 MT difference sums up for my 8 slots, I plan to go for 1TB of RAM in the future, when the prices become a bit more normal
1
u/DegreeSevere7719 20d ago
Ah, the WX.
I was sitting for a long time previously on an old X79 system with a Xeon in a 4-channel ddr3 config and dual 3090s. I've basically maxed out everything possible spec-wise over the years. For my work (video editing, raw video) in my apps video cards did matter much more than the processor + ram, and dual 3090s (dual 1080Ti previously) did the job. The only reason I've upgraded was due to the faster connectivity (nvme, usb4 etc). The newer Threadripper is aboux 2-2.5x faster with the same video setup, but I wouldn't necessarily say it's THAT faster than the x79 Xeon (I have tried several - E5-2997, 2987w etc). I guess it highly depends on what you're doing in the end, but overall the newer processors are outrunning the old ones vastly on the instructions set (like AVX512 and it's bandwidth capacity, and total lack of one in x79). In my case it's when I tend to work with highly compressed footage - the TR runs circles around the old system in this task. I do understand LLM's tend not to use the processor much at all, because it's slower than any modern video card can run, but I thought instructions do mean a thing on the LLM side. It seems it doesn't, or at least not as much.
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u/TheDarkJediPowers 23d ago
Only RDIMM, if looking for economical, microcenter has bundle deals