I had 2x512 of Corsair XMS PC5400 RAM in my system. Recently I got another 2x512 set of the same exact RAM. With the 1G in the system, I had the timings set to 4-4-4-12 (what the memory is rated at), instead of the 5-5-5-15 that my BIOS auto detected. Upon first boot, the computer would not post with all 4 sticks in. So I took the two new ones out, reset the timings, undid my OC settings, and booted with just the 1 G. Put the second Gig in with everything default, and it booted. So I figured that was it.
Wrong!
I was getting random blue screens with the 2G in. Sometimes the computer wouldn't even post, even with the default timings. I took the new RAM out, everything was fine again. So I figured I have a bad stick, or one (or both) of the previously un-used RAM slots on my motherboard were bad. So I took a stick of the original RAM, and booted the PC with just that stick in all 4 slots, and it posted and booted each time. I took each of the new sticks, and did the same thing. One of the sticks, no matter which slot I put it in, the PC will not post. I've never had RAM issues, but that's pretty much a dead on indicator that I have a bad stick, right?
Wrong!
I was getting random blue screens with the 2G in. Sometimes the computer wouldn't even post, even with the default timings. I took the new RAM out, everything was fine again. So I figured I have a bad stick, or one (or both) of the previously un-used RAM slots on my motherboard were bad. So I took a stick of the original RAM, and booted the PC with just that stick in all 4 slots, and it posted and booted each time. I took each of the new sticks, and did the same thing. One of the sticks, no matter which slot I put it in, the PC will not post. I've never had RAM issues, but that's pretty much a dead on indicator that I have a bad stick, right?