new ram problems

[spcguessed]

i've recently bought an extra 2 x 1gb ram sticks for my pc which is currently running on 2x 512mb. when i added the extra ram to the motherboard it began running quite unstable. i've tried the new ram in there on its own and works fine. the mother board is a an Asus p5p800 motherboard that is capable of 4gb of ram so i'm wondering if anyone can explain why the two ram wont run together. the ram is DDR400 PC3200 and the manufacturers are Corsair Value Select (new ram) and Elixir (old ram).

any help would be much appreciated

 

[ProcalX]

make sure in your bios the memory settings are set to Manual (ie you specify them), then i would play around with some of the memory settings.

The problem you have is latencys, your 2 x 512MB will run @ PC3200 2.5-3-3-6 or something like that, where as your 2x1GB will run @ PC3200 3-4-4-4-8 (alot slower), your motherboard is probably setup to run the memory @ the original memories speed, therefore trying to run your 2 x 1GB @ 2.5-3-3-6 (way to fast for 2x1GB).

try setting all your memory to 3-4-4-4-8 2T