I own a Gigabyte GA-K8N SLi motherboard, and currently I have 2x512MB DDR400 DIMMs installed (Crucial Ballistix 2.8v).
Now, I have an older 2x256MB DDR400 kit (GeIL), with corresponding timing specs, but those are suppose to operate at 2.6-2.7 (though it seems people can make them run at up to 3.0v).
The question is, can I mix those with my current RAM, as in one dual channel bank for the 1GB and the other for the 512MB?
There's also another twist, I had my Crucial sticks replaced about 6 months after buying them because of sudden bad sectors.
I figured that the summer's heat combined with the close placement of the sticks on the board might have caused them to overheat, so I didn't want to take any chances and put them far apart, while giving up dual channel.
I've built that same MB and mixed 2 x 1 GB OCZ Platinum and 2 x 512 MB Kingston. Both kits were PC3200. Single channel with all four DIMMs or dual channel with either of the two kits alone was what I found capable. I can't rememeber the data transfer rate with all 4 DIMMs, but it seems like it was 333MHz. or less than the 400MHz. with just two DIMMs alone. Heat was not a problem. I also have 4 x 512 Crucial Ballistic DDR 400 and had a DIMM go out. I attributed that to overclocking and overvolting them. I still use them in another machine.
I tried that, and it seems the board will work with 2x512MB modules in dual mode, but with only one of my 256MB modules.
One off the 256MB modules is causing problems, might be related to the 0.2V+ voltage required to operate the 1GB pair.
In a not so related note, the 2x256MB modules where salvaged from my older system which had it's mobo die and put into my current system before I got the new modules.
Right at the first minutes of operation, loading anything that was over 256MB caused my system to halt completely, and the only way I manged to fix that was to up the DDR voltage by 0.1V, which restored balance to the system.
Now, those modules worked fine in my old mobo with no voltage modification, and it's impossible to say if they were ruined by the old mobo's death.
Either way, do you think it's a smart to have 2x512MB dual + 256MB?