I am considering the old school x3xx and x4xx series here (the ones with real sound volume buttons). This is the generation in between the Evo style and the newer 6910p, x5xx, x7xx series style, which was then followed by the Elitebook 1st generation (xx30) then Elitebook 2nd generation (xx40) series.
HP/Compaq x3xx and x4xx series:
The HP/Compaq x3xx and x4xx series are the competitor of the T60 in terms of FSB & CPU performance,
945GM or 945PM -- 667-MHz FSB Socket M up to T7600@2.33-GHz
This is all SODIMM DDR2 2x2GB shit tops. You can try 2x4GB tho (feedback), no garantee it will work.
Which one has the best graphics ?