Thinkpads Forum

Hey

I have a Thinkpad 600x 2645 4EU from April 1999 with the PIII 500 MHZ processor. I'm just needing a little bit more CPU Power. The PIII 850MHz seems unreasonably expensive at ebay (80 Euro) while you get 650 MHZ for much less. 650 Mhz would still be 30% more power than 500 MHz. Does that work or is there a problem because of the not existing speed stepping or some kind of locking? The air cooling should be the same for all 600x?

Thanks everyone

The quick answer is that yes, you can do a straight swap of CPUs, BUT the new CPU will run at 150MHz less than its maximum speed unless you do some kind of fiddling (i.e. it will run at the same speed as your 500MHz CPU), AND in some cases you may need to hit FN+F2 every time you boot up in order to complete the boot process and bypass a boot error caused by the CPU upgrade.

There are different examples where simply changing the CPU driver have fixed this problem while others have required a hardware mod soldered to the MMC-2 board that the CPU sits on. If you do neither of these things, then your 650MHz CPU will be limited to 500MHz.

A fairly detailed discussion of these confusions is available here:
Can my 600x be upgraded?

Phil.

Ok, that seems to destroy my upgrade plans. Are you sure that every CPU will miss 150MHz or does that refer only to the 850MHz running at 700MHz?

I was able to upgrade my non speed-step 600X from 500 to 850Mhz without too much of a problem.(2646-8EU)

As stated above..there are 1 or 2 small inconveniences...like changing the CPU driver in Windows Device manager and hitting FN-F2 after the splash screen, but my unit does run at 850 Mhz when on main power. I did not have to solder or otherwise physically alter the machine, aside from replacing the CPU. On battery it runs at 700Mhz.

The thread Phil links to was very helpful

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