Originally Posted by
msb0b
As long as the major specs match up, i.e. DDR2, SO-DIMM 200 pin and 1.8V, then it should work. You can have mismatches in the minor specs like the frequency and timing. The memory controller will just use the slower module's timing in order to use both memory modules.
*USUALLY*.
I've had a mismatch that was driving me nuts trying to diagnose as I didn't have the timing info to realize the problem.
When I finally gave up on the board because it wouldn't run reliably with two sticks and got a new board I found out what was up--the new board immediately yelled about one of the sticks not being quite up to snuff.
The original board perfectly happily went ahead and set things wrong--just far enough out of spec that it made the machine unstable.