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There are no "4gb 677mhz"

max ram of 667 mhz powermac is 1.5gb

And what exactly are you comparing?
iBook, PowerBook, powermac? what are the prices?
 
I think the OP is talking about the MHz of the RAM itself, rather than the machine it's going into. I would've thought 4GB of RAM would be better, but I can't promise that. Unless you're talking about taking RAM out of an older machine, why not get 2 x 2GB 800MHz chips?
 
Well, before you will get a reasonable answer, you will have to tell us which machine specifically you are installing the memory in.

imac, but an answer that applies to all computers would be helpful for future reference.
 
imac, but an answer that applies to all computers would be helpful for future reference.

Sigh. There are 8 distinct eras of iMac each of which take different RAM.

You have to be more specific.

And for future reference the answer to this and many other repeatedly asked questions, is in the Guides : Hardware: Understanding Intel Mac RAM

Assuming you are talking about an intel iMac, there are four categories:

CoreDuo machines take 667 MHz RAM limited to 2 GB ( 2 x 1 GB SODIMMS)
White Core2Duo machines take 667 MHz RAM up to 4 GB ( 2 x 2 GB SODIMMS) but will only utilize 3 GB of that total
Aluminum SantaRosa Core2Duo machines take 667 MHz RAM up to 4 GB
Aluminum (April 2008) Core2Duo machines take 800 MHz RAM up to 4 GB

There is no point in installing 800 MHz RAM in a 667 MHz machine, it won't make it go faster and it may crash the machine.
There is no point in installing 667 RAM in a machine that requires 800, if it works at all, it will slow the machine down.
 
Sigh. There are 8 distinct eras of iMac each of which take different RAM.

You have to be more specific.

And for future reference the answer to this and many other repeatedly asked questions, is in the Guides : Hardware: Understanding Intel Mac RAM

Assuming you are talking about an intel iMac, there are four categories:

CoreDuo machines take 667 MHz RAM limited to 2 GB ( 2 x 1 GB SODIMMS)
White Core2Duo machines take 667 MHz RAM up to 4 GB ( 2 x 2 GB SODIMMS) but will only utilize 3 GB of that total
Aluminum SantaRosa Core2Duo machines take 667 MHz RAM up to 4 GB
Aluminum (April 2008) Core2Duo machines take 800 MHz RAM up to 4 GB

There is no point in installing 800 MHz RAM in a 667 MHz machine, it won't make it go faster and it may crash the machine.
There is no point in installing 667 RAM in a machine that requires 800, if it works at all, it will slow the machine down.

It's Aluminium and I got it end of last month, so I'm assuming it takes 800mhz ram.
 
When you purchased doesn't necessarily state which version of iMac you purchased. Did you buy it new from Apple? Was it after the recent update? Reason being, this latest update boosted iMac ram up to 800mhz, so it matters which version you have more than a vague idea of when you purchased it.
 
Yeah...

You're looking at a $15 difference in price between the 800mhz and the 667mhz for 4gb of ram. Why is there even a question if your computer takes 800mhz? Your decision is whether to spend $110 on 4gb or $$50 on 2gb.

Even that is pretty obvious to me. Ram is cheap now, buy accordingly.
 
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