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I have 2 memory sticks, each 1GB, DDR2 operating at 667 mhz. I'm looking to buy 2 GB more, and have two questions:

  1. Should I buy 2 pairs of 1 GB, or 1 stick of 2 GB? Does it make a difference nowadays?
  2. Should I buy 800 mhz or stick with 667 for better compatability?

Edit - given that 800 mhz costs the same as 667, will 800 perform worse than 667? If not, I might as well buy the 800.

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marked as duplicate by slhck Nov 11 '13 at 17:07

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

up vote 7 down vote accepted

If your motherboard supports (and most likely it does) dual channel RAM you should buy 2x1 GB modules.

As for buying 800 MHz - if you combine different speed modules they will operate at the speed of slowest ones. So if you don't intend to change old RAM but only add 2 GB, buy 667 MHz if you get it for cheaper.

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You meant 667, not 6667 :) – ripper234 Jan 1 '10 at 18:56
Solid advice, though I'd check how much the price difference is between 667MHz and 800MHz before deciding. If the price difference is negligible it may still be worth it, if only to make it easier for a future upgrade to lift the speed to 800Mhz. How much that flexibility is worth to you comes down to your situation and future plans. – Adam Luchjenbroers Jan 2 '10 at 0:26
Note my edit - it might be worth to buy 800 anyway if they cost the same. – ripper234 Jan 2 '10 at 6:01
Indeed I meant 667 :) And true, if you get 800 for the same price buy that so you have more options for future upgrades. – T. Kaltnekar Jan 2 '10 at 9:46

go to and use their Memory Advisor tool. select your mainboard manufacturer and model and you will get a recommendation which modules suit best.

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First of all, as molly has stated earlier, run the Memory Advisor tool to make sure that your mother board can even support 2gb sticks of memory (some motherboards can not).

***If you don't care about technicals, please skip to the last paragraph.

Next, look at your motherboard, do you see 2 pairs of coloured slots for your ram (we are assuming that there are 4 slots, if there are only two then your out of luck already)? If there are, that means your motherboard is capable of running duel channel ram, this is where you will need to determine what kind of performance you want and which ram to buy.

Now there are two things to look at, practical performance and cost.

Ill answer your clock rating question first. As for which to buy, 800 mhz or 667mhz, it wont matter interims of performance. Your system will run the ram at the lowest common speed (in this case, 667Mhz). However, 800Mhz ram is much cheaper than 667Mhz (if you buy online). 667Mhz is dated technology, thus a bit less non standard, 800Mhz is more standard now (which means its produced more and cheaper). Buy 800Mhz.

RAM can run under duel channel mode. However, depending on how detailed orientated you are, it may or may not matter to you. 1 pair (2 sticks) runs faster than 2 pairs (4 sticks). Less large capacity chips run faster than many smaller capacity chips.

Lastly, 2GB sticks are cheaper than the equivalent in 1GB sticks by 10-20%.

If you want the absolute best performance, buy a pair of 2gb 800Mhz sticks and throw out the old 1gb sticks. If you want to go with a balance of cost and performance, buy 2 1GB 800Mhz sticks. If you just want low cost and could really care less about performance, buy a single 2GB 800Mhz stick.

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Actually, 667 and 800 cost the same.…… – ripper234 Jan 2 '10 at 5:59
  1. I would recommend buying one 2gb stick. This will make it easier to upgrade again later, because you'll have an additional free slot.

  2. Either should work fine.

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If the motherboard has dual channel, doing this will remove the capability and make the machine slower. – William Hilsum Jan 1 '10 at 15:30

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