I don't know why I didn't see this thread before, it looks like another person was successful with the exact type of RAM that I am trying to use in their 780. Looks like the problem might be with my BIOS update. I'm sure that it is very out of date. I will try updating it. [SOLVED] Dell Optiplex BIOS/RAM question (spiceworks.com)
I have an old dell optiplex 780 that I wanted to upgrade. I bought some ram (M378B5273CH0 - CH9) and it doesn’t work. The RAM is okay, I tested it in another machine. The DIMM slot is okay, I tested with another stick. I get the 3-1-2 beep code for a memory error. My question is… why? How could I have done better research so that this wouldn’t have happened? Where is the information that I should have looked at?
Dell optiplex 780 RAM compatibility