why is rdtsc reporting wrong cpu cycles?

[Marco Correia <mvc _at_ xxxxxxxxxx>]

Hi,

I'm using the following function for getting the number of CPU cycles elapsed 
since I rebooted:

/* Read Timer Stamp Counter */
unsigned long long int rdtsc(void)
{
   unsigned long long int x;

   __asm__ volatile(".byte 0x0f,0x31" : "=A" (x));
   return x;
}

The problem is that the value I get dividing by my processor frequency (my 
computer is a 650Mhz toshiba satellite pro 4340) is giving me about 1 hour 
and I'm using the computer for about 4 fours.

Am I forgetting something obvious? I already googled around but I came to the 
conclusion that only new P4 M processors are able to change speed. 

I'm sorry if this is not the place to ask.

Thanks
Marco

ps: Please CC me as I'm not subscribed

-- 
Marco Correia <mvc _at_ netcabo.pt>

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