Does anyone know if there is any difference in performance between mobile P3 and desktop P3 cpu at same clockspeed? I could not find any benchmark comparisons online.
"Pentium 3" is a marketing name. Technically there were three different CPUs, the Katmai (with 512kB external L2 cache running at 1/2 of the clock speed), Coppermine (with 256kB on-die L2 cache running at full speed) and Tualatin (with 256kB or 512kB of full speed L2 cache).
There was no difference in peformance between similarly clocked CPUs (bus and multiplier) of the same family with the same cache. There were no mobile Katmai cores (or Deschutes for that matter - the later mobile Pentium 2 had a unique Dixon core), a lot of mobile Coppermine CPUs and a good number of mobile Tualatin CPUs (as the early P4 CPUs were singularly unsuited for mobile use), which all had 512kB L2.
If 800Mhz mobile coppermine and 800Mhz desktop coppermine have same performance, where did the reduction of tdp come from?
^Reduced core voltage, mainly. Desktop and mobile CPUs of equivalent silicon differ in that the latter use "cherry-picked" cores that stably run at the same clockspeeds but at a lower voltage.
