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I have 1GB RAM in my machine - two 512MB sticks. When I run Windows Memory Diagnostics with both memory sticks installed it reports errors. If I install just one stick then there are no errors at all. I also tested them using memtest, memtester and the Office Diagnostic tools - the same problem occurs.

I've tried all two possibilities for each RAM (1 stick X 2 slots) and didn't find any kind of problem. When I installed both of them, Windows starts annoying (BSOD). My motherboard supports up to 4GB (2 x 2GB). The RAM modules aren't identical (same make/model).

I've tried to adjust the memory voltage from the BIOS, but with no luck.

What am I missing?

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It could be the memory controller in your motherboard. Try the RAM in another computer and report back. – Breakthrough Sep 2 '11 at 10:24
Have you swapped the around? e.g. tried just one, but the other one? / and in different sockets? – William Hilsum Sep 2 '11 at 10:27
Some motherboards have a dual channel (see wikipedia) architecture, so if you have less RAM sticks than RAM slots on your motherboard, you need to see the user guide for finding out where exactly to plug them. – vtest Sep 2 '11 at 10:34
Did these ever work in this computer? – Ƭᴇcʜιᴇ007 Sep 2 '11 at 13:45
possible duplicate… ? – Nate Koppenhaver Feb 26 '12 at 1:29
up vote 7 down vote accepted

Based on your comment that they are not the same make/model....

If the modules are significantly different enough you can/will run into timing issues between them, which will only be visible when using them together.

Figure out the timing settings of the slowest module, and then hard-set your BIOS to use those timings.

If that doesn't work, then you may have to accept that sometimes RAM modules just don't play nice together, and the motherboard may not be robust enough to make up for the discrepancies.

If you've got other similar modules around you can play the shell game with them until you find a set or two that get along.

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