I have an optiplex 755, a couple weeks ago the PC wouldnt boot. The diag numbers on the front indicated memory issues. I purchased some replacement modules. They arent dell parts, but they are compatible because I've used the same exact models in other 755's. I installed one of the new modules and the pc worked fine. I rebooted the PC and then it died. Lights 3 & 4 which indicate a memory issue. I took out all the, replaced the new RAM with one of the original sticks, the one that didnt fail. That stick does NOT work in DIMM1, but if I put it in DIMM3, the PC works as normal except I get a memory configuration error. I quick F1 keystroke and my PC ignores it and functions as normal. Is there a way to disable DIMM1? or swap to DIMM2 and DIMM4 as normal config?
Did you try installing the new modules in matched pairs? If you didn't, it might not work.
Did you try all modules in slot 1, with all the other slots empty?
Unfortunately, if the modules all work in slot 3 but not in slot 1, you probably have a motherboard failure. There's no way around that except to replace the motherboard. emoticon.Sad.title
Forum Member since 2004
I am not a Dell employee
Thanks for replying. I did try all the matched pairs. The new modules i purchased were both the same. I tried all the working modules I have in DIMM3, but only the original module works. I tried the new RAM in another PC, and it works there, but not in DIMM1 or DIMM3. This is really annoying because the PC works, you just have to hit F1 to ignore the memory prompt.
I also noticed, none of the RAM works in DIMM2 or DIMM4. Kind of a bummer, it would be nice if you could just change the default slots...