In this patch, it mentioned that crystal frequency was a bit slower than expect on Skylake Xeon.
I wonder is this issue only would happen on Skylake Xeon or not?
Because on Cascade Lake Xeon, I haven't find the slow down.
I'm using TSC as the source of timestamp, so it's real important for me to figure it out.
My question actually comes from <Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3> 18.7.3 Determining the Processor Base Frequency, there is a Table 18-85. Nominal Core Crystal Clock Frequency
Xeon Scalable has CPUID signature 06_55H, but they may have different microarchitecture, e.g. Skylake, Cascade Lake.
For Skylake Xeon, there is comment in kernel patch:
All SKX subject the crystal to an EMI reduction circuit that reduces its actual frequency by (approximately) -0.25%
I wonder is there the same issue in further microarchitecture? If there is, which means the Nominal Core Crystal Clock Frequency of Xeon Scalable in manual is not that accurate. So I can't use it as timestamp source.