The TSC runs at "P0 frequency", but I cannot see how to read that from any configuration information in user-space.
Intel processors have the base frequency in the CPU identity string "Intel(r) foo(r) processor @ 99.9GHz", but AMD ones do not. There seems no cpuid leaf which would give me this, and, (on Linux), looking at
/sys/devices/system/cpu/cpuN/cpufreq/ only has max and min frequency files, which, again do not reflect the notional P0 frequency.
Surely there's some way to find this out!?