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I have 8 slots for ram on my motherboard. They are in pairs to take advantage of dual channel memory. Right now, I have 2 1GB sticks of ram, and I'd like to add 2 2GB sticks of ram for a total of 6GB. Is mixing the different sizes of ram going to cause any problems?

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We are assuming you are operating a 64-bit OS to effectively tap on more than 4GB of RAM. – caliban Sep 18 '09 at 16:43
It really depends on the mobo type, I had a Foxconn but it was performing poor with mixed RAMs but then when I used the ECS everything was flawless. – user127088 Apr 7 '12 at 12:10
up vote 11 down vote accepted

No, it won't cause the world to implode, or any problems for that matter. Make sure the 2x1GB and the 2x2GB are installed in corresponding banks to enable dual-channel memory mode.

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Some motherboards are more finicky with ram then others. I had a motherboard that refused a second 2GB set from the same manufacturer. – sakkaku May 28 '11 at 7:53

Yes you can, but personally, I wouldn't.

Ram is so cheap now, you should just dump the 1GB sticks and get another 2x 2GB.

Even if it will work, it is always better (for speed, performance and reliability) to have all matching memory.

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While this answer makes sense logically, sometimes (if not often) money is tight, and buying more just doesn't make sense, when what you have works just fine. – killermist Jun 24 '12 at 16:55

It'll probably work, but the only way to know is to check your mobo manual (or try it). Most mobos let you do that, but I've run across a handful that won't.

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Try to make sure they have matching clock speeds. Shouldn't be any issue.

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Your motherboard is designed with a few companies in mind. It's never really made to support all. So, if you find out with which RAM a motherboard works best, it won't make a difference if you pair 4g with 1g as long as you pair them correctly.

In a 2-slot board, dimm0 is the 4g and dimm1 the 1g. But in a 4-slot board, it will be dimm0 4g, dimm2 1g, dimm1 4g, and dimm3 1g. The numbers may vary, but the RAM slots are colour-coded together say yellow and blue the yellow will be matching set and blue matching set as long as you always out the higher RAM speed and size in the first set starting at dimm0. Last, note that on an 8-slot board, it changes very much unless it supports 4 dual channels. There will be two sets of four with four linked together, so watch out for that.

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There are several technical and grammatical mistakes that prevent this answer from being very helpful. – Ramhound Apr 14 '15 at 18:43

I've always heard you don't want to mix like that espcially if the ram has different CAS timings and the like. I don't like to mix even if it is the same size from two different companies that claim the same CAS.

You'll probably get better performance from the two 2gb sticks in there alone than adding in the other two 1gb sticks with the two 2gb sticks.

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You will definitely get less performance - More RAM is always better. Proven and substantiated by many online resources. – caliban Sep 18 '09 at 16:42
In general I agree with you more RAM is better. But I've just always heard of stability problems when mixing sizes, types, and even companies. – mosiac Sep 18 '09 at 16:48
More ram is better, but more syncronised RAM is better-er :P – Phoshi Sep 18 '09 at 16:57
I had run with mismatched rams for years w/o any p0rblems. – kinokijuf Feb 6 '12 at 16:22

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