Question Using non-preferred ram slots?

M Thompson

Mar 26, 2013
I have an MSI z370 Gaming M5 motherboard that had a ram slot go bad. I initially thought it was the ram itself until I put the stick back in a different slot and all problems ceased. My question is about using non-preferred ram slots.

Most motherboard manuals will have guidance as to which slots to use if you have 1, 2 or 4 sticks. I know this is partially so that you can maintain dual channel memory in boards that support it, but are there any other reasons? With 4 ram slots in a dual channel board there should be 4 different combinations of slots to use 2 ram sticks in that would still use the A and B channels (A1 B1 / A2 B1 / A1 B2 / A2 B2). Why would a board manufacturer prefer A1 B1 over any other combination? Is there any other performance or stability reasons (besides running the memory in dual channel mode) that would make it important to use those preferred slots specifically over any other dual channel configuration?

I haven't noticed any major performance losses compared to before I started having issues, and stability has been just fine, so I'm curious why they would be so specific. Is it just simpler to tell the average user to use X and Y slots rather than trying to explain to them they can use any combination of an A channel and B channel, or is there another reason like power delivery or bandwidth or something that would make it important? I'm trying to decide if I need to buy a new motherboard or go through the RMA process or if I can continue to use the board as-is.
You may get some non-preferred performance.

But really, I think it's just the safest bet considering the length of the traces, how they might or might not be shielded from electronic interference, etc. The manufacturers consider things other than the memory subsystem and things in the environment that might interfere with performance.

I would say that as long as it is running OK, you're good to go - unless you plan on adding more or faster memory in the future. Then you should RMA it while you can.