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Does it make sense to mix different memory modules in one system? I have 2*2GB modules, and now I am considering an upgrade. Should I buy 2 1GB modules, 1 2 GB, or I should go for another pair of 2 GB modules?

I have a Core 2 Quad CPU.

EDIT: I have 4 banks for memory, which leaves 2 empty.

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It depends on your goals.

From your post I deduce that you have at least four memory banks (2 used, and 2 which you consider filling with more memory). If this is wrong (e.g. 6 or 8 banks) than please add that to the original post.

The CPU you mentioned is capable of using memory in dual channel mode. If you use this than your system will be slightly faster. (About 5% for average usage, this will vary per application).

Thus filling your memory banks with pairs of DIMMs would be optimal for speed.

There are two possible reasons not to do this:

  1. Cost. E.g. when 1x 2GB is cheaper than 2x 1TB.
  2. When you intend to leave one socket free for future expansion. (If you fill all banks now then you will have to discard some when you next expand the memory).

If these are relevant to you or not is something you will have to decide for yourself.

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Thanks for your answer. I have 4 banks in total, so 2 are free. I don't think I want to leave any bank empty, because the next planned upgrade will be to change the CPU and motherboard as well, just wanted a cheap upgrade now. – Grzenio Jan 9 '13 at 10:33
I just wanted to clarify - is adding 2x1GB worse (i.e. slower) than adding 2x2GB? – Grzenio Jan 9 '13 at 10:34
No, assuming both 1GB and 2GB have the same specs it will be just as fast to access memory. – Hennes Jan 9 '13 at 13:51

In general, if you have the budget, upgrade by getting the most memory per module. (1 2gb is better than 2 1g modules). This is better because if you want to upgrade in the future, you will have more slots available. That being said, you already have 4 gb of memory which is plenty, unless you are running out of memory of course.

I would go with 1 2gb.

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I think it's more efficient to have more memory clips for the same total amount of memory. I think they work faster this way. Makes sense, in a way. 2 GB of memory can either circulate through one port, or through two ports. Two ports, more room for data, or something. Also, I think they're supposed to work together.

Apparently, in pairs, they have more potential. So I think ideally, you should get 2 x 2 GB. Then you'd have four of the same. Or so I was told. I think. I'm not sure about those two first paragraphs.

Also, I'd like to add a comment about DDR2 memory. The demand for it is decreasing rapidly, which makes it expensive. Sometimes, illogically, you'll even see 2 GB of DDR2 more expensive than 2 GB of DDR3, for example.

Considering that more-than-decent motherboards with DDR3 capability and much more are not so expensive (my ASRock 970 Extreme3 cost me 150 $), if I were you, I would consider upgrading the motherboard and getting DDR3 memory. You'll pay a bit more, but I think it's definitely worth it.

Edit: Oh, riiiight, that's what Hennes said. Dual channel memory. Two of the same memory clips working better together. I knew I wasn't crazy.

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1<sup>st</sup> paragraph: Almost, but not quite. It depends on the capability of the memory controller if more channels can be used. For core2 systems they can use up to two DIMMs at the same time. (for other systems it varies. E.g. an i7 920 can use up to three). For that multi-channel usage they need to be the same size and it will use the slowest setting of the set. In the OPs case (s)he has 4 sockets and can use up to two pairs. – Hennes Jan 8 '13 at 21:28

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