EPYC 7452 CPU's - Showing Very Slow L3 Cache and RAM in memtest86

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RCS

New Member
Jul 27, 2018
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Is there a reason that L3 cache and RAM would show speeds this slow in memtest86?

I have two of these systems and both are showing the exact same results.

amd.png

Gigabyte G482-Z52 systems
2x EPYC 7452 CPU's
16 DIMMS of DDR4 2933MHz (1 DIMM per channel for each CPU, so should be at full 8 channel memory)

The speeds seem WAY below what they should be.

I've tried playing with the NPS settings in the BIOS with no difference. 1 DIMM, 2, DIMMS, up to 8 DIMMS per socket, also has the same result.

Is it possible memtest86 isn't capable or optimized to test speeds with EPYC systems?
 

RCS

New Member
Jul 27, 2018
19
2
3
FYI - For RAM speeds, sysbench in Ubuntu is showing double the speed (32GB/s read) with only 4 DIMM's installed currently (so dual channel)
It shows approx the same speed for write.

amd2.png

Still don't understand the odd L3 cache speed, but I'm assuming it has something to do with how the NUMA nodes work and share L3 cache.
 

hmw

Well-Known Member
Apr 29, 2019
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I wouldn’t use memtest to measure cache speeds. Use lmbench or intel MLC or TinyMemBench

For memory throughput - use STREAM

these benchmarks need a lot of reading to see what you’re doing and how to setup properly + interpret results correctly.
 

codyrawls

New Member
Oct 9, 2020
1
0
1
I wouldn’t use memtest to measure cache speeds. Use lmbench or intel MLC or TinyMemBench

For memory throughput - use STREAM 8 ball pool

these benchmarks need a lot of reading to see what you’re doing and how to setup properly + interpret results correctly.
Thank you very much!! Very useful advice
Regards,
 
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