Latitude Cpi

I'm giving this trusty old machine to my mum as i'm getting a new laptop, but first I want to speed it up a bit, from what I've gathered reading online I have two choices of cpu, either a 650mhz celeron or an 850 P3, but then it wouldn't run at 850 becuase the motherboard isn't speedstep compatible. I'm not sure which would work out quickest from the two as I can't get a definitive answer as to what speed the P3 would run at. The next thing i'm un-sure of is memory. Now becuase this is the CPi R-series it doesn't need the EDO memory but instead runs normally at pc66, I've run through the system using cpu-z etc. and it would appear the memory chips in there are PC100's slowed down to 66, sadly there's no obvious description on the chips themselves but what I'd like to know is how fast a module can I put in? Obviously they're all gonna get slowed down to 66 but PC133 is much cheaper than PC100 etc.

Here's the technical info. http://support.euro.dell.com/support/edocs/systems/pcor/en/en_ug/specs.htm

 

I really doubt that any performance gain is going to be worth any money...I mean, you'd get a better gain from upgrading the RAM rather than the CPU so do RAM first, but I do not think it will be a very significant difference in performance.

 

I realise it won't affect it too much but when the cpu's cost so little I may as well. I've also realised that being that I was half asleep when writing this, I've gone and put it in the wrong forum, would a mod please be so kind as to move it to the general dell forum.