I have a Biostar - TForce 6100-939 (with an AMD 4000+). The MoBo has 4 RAM slots. I previously had 2 1gig PC3200s and just received 2 1gig PC2100s (received from a cmoputer that was being scrapped). As the memory chips are of different speeds, what is the best placement for the 4 chips in the 4 slots (DIMMA1, A2, B1, B2)? Is it even worth installing the second two, slower chips?
When memory of different speeds is installed, memory speed and timings will be set to what ever the slowest memory can run at.
If you already have 2 gig of memory, installing more memory, even more PC3200 is not going to make any noticable difference. Installing slower memory will most likely cause a noticable decrease in performance. Some boards may not like the mixed modules and not even boot. In short, I would not install them.
If on the other hand you only had say 512 meg and were adding another 512 meg, then I would say give it shot. The added memory would be beneficial even though it would be running slower.