Is there a way to determine the time taken from power on to Windows starting

I would like to be able to tell how long it takes to get from power on to windows starting. Is there a way of determi开发者_C百科ning this retrospectively (ie once windows has started)? Does the BIOS/CMOS hold a last boot time? Would it be possible to tell from RDTSC how long a machine has been running for and subtract the windows boot time?

You might try BootTimer or BootRacer to see either of them will do what you want.

I don't believe you can determine this after Windows is started. I'm not aware of any BIOS that stores the last boot time. But on any modern machine, if the time between power on to calling the OS boot loader (essentially the time it takes to run the POST routines) takes longer than a few seconds, something is wrong.

Are you trying to do this programmatically to get the accurate amount of time that the machine has been online and usable? The inaccuracy resulting from the few seconds that POST takes doesn't seem like it would make a significant difference. If you're timing for benchmarking or optimization purposes, either of these two utilities should work for you.

Get the time since power on from GetTickCount(). Then get the timestamp of a file Windows touches at boot (windows\bootstat.dat for example). Code is below. On my machine it says 16 seconds which sounds accurate.

#include <stdio.h>
#include <windows.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <time.h>

int main()
{
    struct __stat64 st;
    _stat64("c:\\windows\\bootstat.dat", &st);

    return printf("%d\n", st.st_mtime - (time(NULL) - GetTickCount()/1000));
}