[fpc-devel] rdtscp

[Marco van de Voort]

In our previous episode, Martok said:
> Tangent: On Windows, RDTSC is wrapped by the QueryPerformanceCounter() call. QPC
> incidentally is complicated enough that it is very likely no out-of-order
> instructions are pending by the time it gets to actually executing RDTSC, but
> with less jitter than "abusing" CPUID for serialisation (QPC takes a rather
> stable 22 cycles). /Tangent

Afaik Query* also works reliable on systems with multiple processors. Might
be important now that Ryzen is a multiple die solution.