Ram: Different size sticks?

sjpetry

macrumors 65816
Original poster
Oct 28, 2004
1,195
0
Tamarindo, Costa Rica
Sorry if this have been asked before (I did a quick check).

I have a iMac G5 with 256Mb stock Ram and I am about to get a 1Gb stick for the second slot. I remember something that if the two sticks weren't the same size that it would be slower (Is this true?). If it would be slower with two chips would the extra 256Mb balance it out?

Thanks for helping. :)
 

jsw

Moderator emeritus
Mar 16, 2004
22,910
41
Andover, MA
Everything I've read points to only minor speed differences, if any, under most use cases. I'm sure the extra quarter gig will more than offset any imbalance, because, no matter how much unmatched RAM is slower than paired RAM (only a tiny bit, BTW), it's still vastly faster than disk. And to be matched it has to be pretty much literally two identical sticks - same size, model, maybe even batch.

I wouldn't sweat it.
 
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Bear

macrumors G3
Jul 23, 2002
8,089
4
Sol III - Terra
In an iMac, one stick of RAM and 2 sticks unmatched run at the same memory access speeds.

You need 2 matched sticks of RAM to get the speedup.

So use both sticks, you'll have more memory at no reduction of what your memory access speed would be with just one stick.
 
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sjpetry

macrumors 65816
Original poster
Oct 28, 2004
1,195
0
Tamarindo, Costa Rica
jsw said that if I get another 1Gb chip that it may not get the speed increase and that it would have to be the same exact one (Is this correct?).
 
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jsw

Moderator emeritus
Mar 16, 2004
22,910
41
Andover, MA
sjpetry said:
jsw said that if I get another 1Gb chip that it may not get the speed increase and that it would have to be the same exact one (Is this correct?).
I forget exactly what "matched" means, but, yes, essentially I think you need to buy them at the same time as a matched pair. But, really, the speed difference is trivial in most situations. You could pony up the $$ to buy two matched 1GB sticks, but you'll spend a lot less (well, half) buying just one and going with 1.25GB - which will be faster than 1GB with two matched 512MB sticks most of the time with multiple apps running.
 
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Bear

macrumors G3
Jul 23, 2002
8,089
4
Sol III - Terra
sjpetry said:
jsw said that if I get another 1Gb chip that it may not get the speed increase and that it would have to be the same exact one (Is this correct?).
You have to get two with the same specs. They don't necessarily have to be bought at the same time.

And actually what the iMac G5 is looking for it really memory that meets it specs and both sticks are the same capacity to get the speed improvements. but the closer the sticks are to each ither in all specs the better.
 
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