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Processors

cyring
Adept II

Ryzen 3950X Suspend/Resume performance counters issue

As investigated, APERF and MPERF counters are messed up when Processor is resuming from S3

rdmsr -aX 0x000000e7
FFFFFFFFC0E01292
FFFFFFFFD3BFDE0D
FFFFFFFFC28CD6A6
FFFFFFFFC111C53A
FFFFFFFFC4B5D257
FFFFFFFFC1D4DC30
FFFFFFFFCA59D1F6
FFFFFFFFDF2B868A
...

The same happens consequently with the read-only counters: 0xc00000e7 and 0x000000e8

The obvious software fix would be to reset counters with a zero write

wrmsr -a 0x000000e7 0x0 ; wrmsr -a 0x000000e8 0x0

However instruction latency won't guarantee a perfect synchronization of all Cores' counters.

 

I would suggest AMD to fix this in a future microcode

 

Regards

CyrIng

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