I couldn't find any clock drift RNG code for Windows anywhere so I attempted to implement it myself. I haven't run the numbers through ent or DIEHARD yet, and I'm just wondering if this is even remotely correct...

void QueryRDTSC(__int64* tick) {
    __asm {
        xor eax, eax
        cpuid
        rdtsc
        mov edi, dword ptr tick
        mov dword ptr [edi], eax
        mov dword ptr [edi+4], edx
    }
}

__int64 clockDriftRNG() {
    __int64 CPU_start, CPU_end, OS_start, OS_end;

    // get CPU ticks -- uses RDTSC on the Processor
    QueryRDTSC(&CPU_start);
    Sleep(1);
    QueryRDTSC(&CPU_end);


    // get OS ticks -- uses the Motherboard clock
    QueryPerformanceCounter((LARGE_INTEGER*)&OS_start);
    Sleep(1);
    QueryPerformanceCounter((LARGE_INTEGER*)&OS_end);

    // CPU clock is ~1000x faster than mobo clock    
    // return raw
    return ((CPU_end - CPU_start)/(OS_end - OS_start));

    // or
    // return a random number from 0 to 9
    // return ((CPU_end - CPU_start)/(OS_end - OS_start)%10);
}

If you're wondering why I Sleep(1), it's because if I don't, OS_end - OS_start returns 0 consistently (because of the bad timer resolution, I presume).

Basically, (CPU_end - CPU_start)/(OS_end - OS_start) always returns around 1000 with a slight variation based on the entropy of CPU load, maybe temperature, quartz crystal vibration imperfections, etc.

Anyway, the numbers have a pretty decent distribution, but this could be totally wrong. I have no idea.