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What are the price differences? I'd go with 2x1GB. I've seen the G.Skill RAM for about $80 on Newegg, could be lower now...
 
What do you mean, better?

Assuming that your machine is a Core2Duo:
2 x 1 GB gives you Dual Channel access, which is 6% - 8% faster on average. IF you don't load up more than 2 Gb of programs and data.


1 x 2 Gb SODIMM gives you the opportunity to go to 3 Gb RAM -- which means that you lose out on the Dual channel 6% - 8%, but stand to gain more performance than that if you are regularly using more than 2 Gb of programs and data, or are using programs like Photoshop that can exploit 3 Gb RAM for faster caching.

There is a Guide on this ... and this is the 24th Intel RAM thread...
 
What are the price differences? I'd go with 2x1GB. I've seen the G.Skill RAM for about $80 on Newegg, could be lower now...

the 2x1GB is like $700 and the 1x2gb is $500 hundred dollars, so if i get the highest end imac without configuring it, keep it on the 2x1Gb memory stick, and also buy 1x2GB memory, and put it in the imac, is that possible?
 
the 2x1GB is like $700 and the 1x2gb is $500 hundred dollars, so if i get the highest end imac without configuring it, keep it on the 2x1Gb memory stick, and also buy 1x2GB memory, and put it in the imac, is that possible?

Oh no -- do NOT buy RAM from Apple. Choose the lowest stock memory configuration from Apple, and add the RAM yourself from a reputable third party seller

Guide on Buying RAM

So if the machine comes with a 1 Gb single module (which most new iMacs do) then you can add the 2 Gb module yourself.
 
the 2x1GB is like $700 and the 1x2gb is $500 hundred dollars, so if i get the highest end imac without configuring it, keep it on the 2x1Gb memory stick, and also buy 1x2GB memory, and put it in the imac, is that possible?

Wow, don't look at the prices for RAM through Apple, it's scary. Check out Newegg or OWC. Yes you could put in the 2GB stick but you'll need to sell the 1x1GB stick cause there are only 2 slots. If you do have the money, get 2x2GB.

Also, OWC and others have tested dual-channeling with 2x1GB and 1x1GB with 1x2GB (3GB total) sticks on a Macbook. The results were that dual-channeling was not affected and 3GB RAM in Macbooks run just fine.
 
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