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I have an Asus M2N-E motherboard, currently with (qty 1) DDR2 module Kingston KVR533D2E4/1G. The board has 4 total slots.

Going to upgrade and I'm wondering if I can mix sizes -- can I add a 2G module and keep the existing 1G?

Thanks.

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up vote 4 down vote accepted

Yes. You can have different sizes, and even in most cases, different speeds (Not suggested though). The only thing to really look out for is that they are compatible. If you're putting in the same brand/model, just different size, I wouldn't see a problem.

EDIT: This may also be helpful: Can I mix and match RAM?

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Yes, I'm going to put in the same model just sized up: KVR533D2E4/2G. Thanks! – bstpierre Nov 13 '09 at 15:24
    
I may have added an edit after your comment... Hopefully you noticed the attached link. – Sivvy Nov 13 '09 at 15:26

You can. However, do notice that on dual-channel memory board, this will decrease memory access speed.

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Thanks for the advice. Is it a severe penalty? I was going to install a single 2G module @ 533, but if the mixture is going slow things down, maybe I'll dump the 1G and get 2x2G @ 667 or 800... – bstpierre Nov 13 '09 at 16:49
1  
Not a severe penalty, but in order to have Dual Channel, both sticks need to be nearly identical (Size and speed). Mostly what you'll be losing out on is the additional bus bandwidth. It's nice, but its your choice if you want 3Gb or faster 2Gb or 4Gb. DDR2 is cheap these days. – Sivvy Nov 13 '09 at 16:54
    
I'm getting to where I end up hitting swap on a daily basis, which is painful -- have to go through and prune out processes that aren't in active use... I think even "slow" 3Gb will not hurt too bad. – bstpierre Nov 13 '09 at 18:48
    
I'd just go to 3Gb, then upgrade to 4Gb as soon as you can. 32 bit Windows will only use a little over 3Gb, but the Dual Channel is helpful, and it isn't really a waste, since the kernel still gets to access the additional RAM for hardware/BIOS stuff. – Sivvy Nov 13 '09 at 19:50

Quick Answer:

If the only difference is in size then likely Yes! Check Asus M2N-E motherboard - Memory/Device Support page for compatible memory modules.


Detailed Answer:

Typically your motherboard manual will indicate compatibility with different memory modules and some order in which to populate the DIMM slots. Motherboards which support Dual-channel architecture can run two or more DDR type memory modules in dual-channel configuration. Theoretically, dual-channel configurations double the memory bandwidth when compared to single-channel configurations though it would seem that this may result in little to no real world performance increases (see this article)

DIMM Socket Color Codes:

Motherboards supporting dual-channel memory layouts typically have color-coded DIMM sockets. Coloring schemes are not standardized and have opposing meanings, depending on the motherboard manufacturer's intentions and actual motherboard design.

Matching colored DIMM sockets may indicate one of two possibilities depending on the motherboard:

  • Matching colored sockets belong to the same channel and indicate that DIMM pairs should be installed to differently colored sockets

  • Matching colored sockets belong to different channels and indicate that DIMM pairs should be installed to the same color.

Guidelines for dissimilar memory modules:

  1. Modules rated at different speeds can be run in dual-channel mode, although the motherboard will then run all memory modules at the speed of the slowest module.

  2. Some motherboards, may have compatibility issues with certain brands or models of memory when attempting to use them in dual-channel mode. For this reason, it is generally advised to use identical pairs of memory modules (matching capacity (eg: 1024MB), Speed (eg: PC5300), CAS Latency, Number of chips and sides, etc.)

  3. For maximum performance, populate the sockets so that the memory capacity is spread as equally as possible between two Channels. A matched pair of memory modules may usually be placed in the first bank of each channel, and a different-capacity pair of modules in the second bank. eg: 2x 2GB DIMMS in Channel A and 2x 1GB DIMMS in Channel B.

  4. For systems with only 1 DIMM socket you have no option (runs in Single Channel mode)

  5. For systems with 2 DIMM sockets place the largest memory capacity DIMM into the first DIMM socket i.e. Channel A, Bank 1 and the second in Channel B, Bank 1.

  6. For systems with 3 DIMM sockets place the largest memory capacity DIMM into Channel A, Bank 1, place the second largest memory capacity DIMM in Channel B, Bank 1 and the third DIMM in Channel A, Bank 2

  7. For systems with 4 DIMM sockets place the largest memory capacity DIMM into Channel A, Bank 1, place the second largest memory capacity DIMM in Channel B, Bank 1, the third largest memory capacity DIMM in Channel A, Bank 2 and the fourth in Channel B, Bank 2.

References:

  1. Asus M2N-E motherboard - Memory/Device Support page

  2. Tom's Hardware - "Parallel Processing, Part 2: RAM and HDD"

  3. Multi-channel memory architecture

  4. HP Support

  5. Lenovo Support

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