SM 1U Epyc 3251: the good and almost good.

Forumula

New Member
Oct 11, 2019
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I just replaced a SM Xeon-D 1541 motherboard (X10SDV-8C-TLN4F) in a 1U SM 5018D-FN4T server (chassis: CSE-505-203B) with an Epyc 3251 board (M11SDV-8C-LN4F). The Xeon-D is being RMA'ed and out of cross-ship warranty. SM wouldn't make an exception so I decided to treat myself to a new board. I know, I am rewarding SM for being stingy with the cross-ship. Oh well :)

Pro: The Epyc board is a drop-in replacement for the Xeon D board (I/O shield and fan location is identical).

Minor con: The dongle SM provides for connecting the ATX PSU to the motherboard (only to keep the PSU happy) is too large and the leads are too short. It is physically impossible to fit it into the 1U case (see attach photo with heatsink for comparison - that giant connector is for four leads only (!)). I ended up removing the pins from the dongle and the ATX power connector and directly connecting them with some heatshrink to keep them together and prevent shorts (see second photo). Then the ATX power connector can be tucked out of the way since it is no longer needed, and everything fits nicely in the CSE-505-203B chassis.

A couple of observations:
- For my workloads the EPYC 3251 is about 15% faster than the Xeon D 1541 that it replaces.
- However, I am only seeing 2.8GHz all-core boost. Advertised is 3.1GHz. Is anyone else seeing this? Are there BIOS tweaks? It's not a thermal throttling issue because if I set the fans to full speed the CPU temp drops to 53C or so but I am still stuck at ~2.8GHz. I am running on 2133 memory but I wouldn't have thought that would affect the all-core boost. I was concerned that the SATA headers in front of the fans would interrupt airflow, but it seems not enough to make a difference. I have all 4 SATA ports occupied and as above I can get the temperature down to the 50s at full load.

Overall the M11SDV-8C-LN4F is great value (I paid $720 on Amazon). But it would be great to hit 3.1GHz on all cores if I can.

[Edit]: See update below. Now running at 3.1Ghz all core boost.



 
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Forumula

New Member
Oct 11, 2019
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Look the TDP setting in BIOS and up it to get maximum boost.
Thankyou! Worked a charm. I set it to 75W (manual says factory is 55W). I also noticed a "Determinism Slider" setting in the same BIOS section and I went ahead and set that to "Power " (default is "Performance"). I don't know if that also affects boost, but it seems Performance mode is only for reproducibility of benchmarks, which I don't care about.

Now hitting 3.1Ghz consistently all-core boost. About 30% better performance on my workloads over the Xeon D-1541. CPU temp pegs at 63C at full load if I max out the fans (vs low 50s previously). Seems like there may be some room to overclock this thing, if that's possible.

I don't know if it's just a better heatsink and airflow, but the Epyc runs a lot cooler than the Xeon D 1541s at full load (they're always in the 80s and that's with a mylar shroud and an extra fan compared to the stock) .
 

Rolando

Member
Aug 8, 2019
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By any chance are you using VMware esxi on this setup? If that’s so, can you comment about compatibility and support with this CPU? Thanks!