You can put whatever combination you want, 2 256's, all 3 128's or two 128 and one 256. If you bought one stick of 512mb that would work too.
I have an IBM 6862 300PL system running XP Pro P3 550 MHZ processor -there are 3 memory slots - 2 full with 128 MB memory strips- the total my system can run is 512MB- my question is....can I install a 256 MB strip or should I stick with 128's in all slots, will they work together?
Crucial says the memory is SDRAM PC133 (don't know if that makes a difference but thought I'd include it).
Thanks for any help.