P4 2.6Ghz running at half speed


Nov 7, 2008
Recently I tried to install a P4 2.6Ghz on my Asus P4s533-x mobo, but it only runs at half speed. CPU-z and a stresstest indicate it's really running only at 1.3Ghz, so it's not a power-scheme-issue or something similar.

Now, for what I've understood while trying to oc this CPU, my mobo wont let me pick a FSB higher than 166. Multiplier is greyed out (which is quite common with P4's) and set to 13, thus when FSB is default set to 100, the speed is correctly displayed at 1.3Ghz. I can set it manually to 133, which gives me a speed of 1.73Ghz.

I've read somewhere that the FSB-speed in the BIOS is actually multiplied with 4, so that suggests the actual FSB-speed would be 533 when set to 133 in the BIOS. CPU-z indicates FSB-speed as 133, but also an actual value of 533, when the CPU runs at 1.73Ghz.

My mobo only supports a FSB-speed of 533 max, so that would mean I will never be able to run this CPU at 2.6Ghz (or even higher :)). :sweat: Is that correct?


Apr 2, 2008
DFGum, sounds similar but thats below the speed step threshold.

It sounds more like his got a 200mhz x 4 FSB chip in a motherbardboard that maxes out at 133mhz x 4. Some overclocking the motherboard's FSB might help but thats also a bit dicey.