PC with 2 RAMs of different frequencies (1GB 533MHz + 2GB 667MHz) showing only 2GB RAM

ddr2memory

I have 6 years old PC with 1.25GB (1GB + 256MB) of DDR2 533MHz RAM. As computer has become very slow and memory usage reaching its limits most of the times, i decided to upgrade RAM. But unfortunately, im not finding retailers selling DDR2 533Mhz RAM near my area.

Since I was not sure mixing up RAMs of different frequencies, i searched in web. Most results said they can be mixed but computer would run at lower frequency of the 2 RAMs. So I bought 2GB DDR2 667Mhz RAM expecting my pc to have 3GB RAM running at 533 MHz.

But computer properties page shows only 2GB RAM. BIOS settings too show the slot with 2GB 667MHz as ACTIVE and other slot with 1GB 533MHz as "NOT INSTALLED". When I removed 2GB RAM, they computer shows only 1GB RAM. So for some reason, 1GB RAM is not getting detected/used.

What is the problem here?

thanks in advance.

Best Answer

Your motherboard could have a low maximum of total memory, 2 Gigs in your case. Otherwise your modules could be incompatible with each other. There some possible reasons and usually it is all about motherboard restrictions. For instance it might not support both single-sided and double-sided modules simultaneously. Other typical problems:

The "problem" is simply that different computer motherboards can accept memory in different, but specific, combinations. Some examples:

  • Some require that all memory sticks in the computer be identical. So if you have four slots, you can have 4x256meg, or 4x1gig, but you can't mix the 256meg and 1gig sticks.

  • Some allow you to mix, but you must mix in pairs. Meaning you might be able to have 2x1gig and 2x256meg.

  • Some require that if you mix, you must do so in a certain sequence. So you might be able to put 1gig in slot 1, and 256meg in slot 2, but not the other way around.

  • Many require that if you mix (according to whatever other rules there might be), the memory sticks share certain other characteristics, such as speed or others.

So, at least try to rearrange modules in different ways.

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