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Comment by bitL | Hacker News Reader

64c EPYC with 3.4TFlops - wow! That's GPU territory!

Linus Tech Tips was actually able to play Crysis using CPU rendering for the graphics: https://www.youtube.com/watch?v=HuLsrr79-Pw

Actually I'm pretty sure the Rome numbers are for double precision whereas most numbers quoted for GPUs are for single precision or less, making Rome's 3.4tf even more impressive.

Half of Titan V/V100 FP64 sounds unbelievable! Can't wait to get my hands on 64c Threadripper with TRX80!

Yea I can't wait for the announcements to happen in the coming weeks. So far the best rumours I've seen seem to have them topping out at 48c for the new TR line, but none of them have been particularly authoritative looking, just that there haven't been leaks of anything looking at 64c yet. I suspect that what might happen is that they'll announce with up to 48c but then a few months down the line they'll announce the 64c cpu. That would line up well with what looks like caused the delays with them not being able to get the quantity of the chiplets they need. They'd be able to frontload all the lower core count demand and then when they don't need nearly as many of them start making the larger ones.

I really hope 32c would work with my Zenith Extreme x399, and 64c with 8-channel TRX80/WRX80. So I could upgrade old TR with a 32c Zen 2-one and buy another 64c with 4TB ECC LRDIMM for some Machine Learning tasks. I am also fine if AMD decided to do 64c TR with Zen 3 only (4xSMT?). But based on Blur ad, I guess they are going to release 64c TR based on Zen 2 as well, just to completely obliterate Intel in HEDT, even if it costs $5000.

Yea the x399 compatibility will decide when my upgrade happens. The Zen+ TRs weren't enough for me to justify but the Zen2 ones seem like they've finally hit. If I need to do a motherboard and other upgrades that'll delay me doing so for a while (need to see how PCIe passthrough and other stuff settles out with the new chipsets) but in either cases I'm going to end up upgrading to this next gen one way or another.

How much does threadripper usually cost relative to epyc for same # of cores?

20-30% usually. You get faster cores but no LRDIMM (i.e. you are constrained effectively to 128GB ECC UDIMM, at best 256GB ECC UDIMM if you are lucky to get 32GB ECC UDIMM modules). EPYC has 4TB ECC LRDIMM ceiling, new TR on TRX80 might have the same ceiling as well. I am glad that AMD provides TR as they make way less $ on them than on EPYC, but it's a great marketing tool for them. I am running some TRs for Deep Learning rigs (PCIe slots are most important) on Linux, and they are great, Titan RTXs and Teslas run without any issue, but Zen 2 should give me much better performance on classical ML with Intel MKL/BLAS in PySpark/SciKit-Learn, so I can't wait to get some.

Naive question: Are you able to use MKL on an AMD chip without jumping through too many hoops?

Yes, just pip install ..., but it's 2x slower than on Intel for Zen/Zen+. Only Zen 2 is close to Intel.

Intel makes rather pessimistic assumptions about AMD and uses the model name to pick which code path to use and ignores the CPU flags for floating point, etc.

So if you want to compare performance fairly I'd use gcc (or at least a non-intel compiler) and one of the MKL like libraries (ACML, gotoblas, openblas, etc). AMD has been directly contributing to various projects to optimize for AMD CPUs. They used to have their own compiler (that went from SGI -> cray -> pathscale or similar), but since then I believe have been contributing to GCC, LLVM, and various libraries.

Yeah, still, Zen 2 is much faster in OpenBLAS and is faster in MKL than Zen/+ as well.

It's lumpy and depends on exactly when you ask.

If shopping I'd compare the highest end Ryzen + motherboard and the lowest end Epyc single socket chip and motherboard and try to guesstimate that price/performance for your workload.

Generally the Threadrippers seem like a much lower volume product and the motherboards are often quite expensive (for the current generation). Both Ryzen and Epyc enjoy significantly higher volumes.

Keep in mind that Threadripper has twice the memory bandwidth of Ryzen, but half the memory bandwidth of Epyc.

Why not just get the 7702p?

I guess TR will be a bit cheaper and higher clocked? And I don't really care that much about ECC errors for ML.

For reference (because I didn't know the comparison):

MI60 has 7.4 TFLOPs double precision at TDP=300W.

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