Epyc Rome - compatible with ECC DDR4 2400 or 2133?

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nutsnax

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Nov 6, 2014
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I'm looking at using ECC DDR4 2400 with an Epyc - should this work? Or even 2133?
 

nutsnax

Active Member
Nov 6, 2014
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ECC DDR4 - you mean RDIMM right ?
best is 2666 but better 2400 than 2133
2400 is degraded to 2133 if you install two DIMM per channel.
Yes RDIMM, just wondering if Rome will work with 2133 or 2400. I need buckets of RAM on the cheap and lower latency more than big fat bandwidth
 

alex_stief

Well-Known Member
May 31, 2016
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You won't get lower latency with slower memory.
But 2400 or 2133MT/s can work, provided the memory is not incompatible for other reasons. On the top of my head, I can't recall any instance of CPUs in recent years that were outright incompatible with lower memory transfer rates.
 
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bayleyw

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Jan 8, 2014
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Works fine with 2400, I've never tested 2133. Rome is sensitive to memory speeds though, since FCLK scales with memory speed; I think this may be the only time in...recorded history where memory speed and channel population can make a tangible (>a few %) impact on performance.

Xeons behave well as you scale the channel count and memory clocks but Rome exhibits pathologies, I briefly had a Rome system with only 5 channels populated and one of my homegrown HPC codes (which was not bandwidth-sensitive) lost half its performance. Such is the hazard with buying AMD...
 

nutsnax

Active Member
Nov 6, 2014
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Works fine with 2400, I've never tested 2133. Rome is sensitive to memory speeds though, since FCLK scales with memory speed; I think this may be the only time in...recorded history where memory speed and channel population can make a tangible (>a few %) impact on performance.

Xeons behave well as you scale the channel count and memory clocks but Rome exhibits pathologies, I briefly had a Rome system with only 5 channels populated and one of my homegrown HPC codes (which was not bandwidth-sensitive) lost half its performance. Such is the hazard with buying AMD...
Thanks for that info, I got a very good deal on a set of 2133 DIMMS as the price jump (nearly 2x) didn't justify the cost for me to go to 2400 much less 3200. I got these 64GB dimms for $55 each so I loaded the boat. I figured more channels would beat out higher speed with fewer dimms anyway.
 

Kizune

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Dec 2, 2022
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Works fine. I even used to just set it preferences to ignore POR and set the speed manually. Then I used very good 8x16gb kit of Samsung ddr4-2400 as 3200. Your mileage may vary but most 2133 ECC kits I had worked fine at 2666 and most 2400 can be overclocked to 2933. CPU was Rome 7742 and motherboard was Asrock Rack ROMED8-2T.