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[SOLVED] CROSSHAIR 8 X570 : Quest for a perfect Base Clock of 100 MHz

contact1
Level 8
Hello,

I'm measuring the BCLK of the Ryzen 3950X using its Core TSC
( an algorithm of two instructions RDTSCP elapsed by one second )

Results are 99.8 MHz on any Core, which is lower than the Processor factory 100 MHz.

After refining my TSC measurements by removing the inherent cycles of RDTSCP, setting the P-State to a fixed ratio, and all possible programming improvements; I'm still getting a estimated Base Clock of 99.8 MHz.

Thus I have questioned the BIOS and I went into the UEFI settings to change the BCLK from 100 to 100.0625 MHz (the first step above 100) ; save, reboot, and measure the TSC to get a coherent frequency of Cores at ~ 3502.2 MHz (35 * 100.0625)

Next, I changed back into UEFI the BCLK from 100.0625 to 100.0 MHz ; save and went straight into measurements to get an almost perfect Cores frequency of 3500 MHz :cool:

Unfortunately, the following boots restored the BCLK to an estimation of 99.8 MHz :mad:

Question is how to manage the BIOS to retain the willing Base Clock of 100 MHz ?

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contact1
Level 8
Disabling SPREAD SPECTRUM has solved the issue. I did it on VRM and SB and now my BCLK perfectly reports 99.9 - 100 MHz

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CoreFreq monitoring at github.com/cyring/CoreFreq