iMac G5 memory upgrade for fast Tiger (future Leopard)

[icibaqu]

I have a 20" iMac G5 2.0 Ghz w/ a 512 stick running Tiger and am at the point where I'm going to upgrade the RAM for badassness, and running the iLife apps, photo editing, and fast-user switching happily w/o much lag and w/ very few beachballs (if any).

I did the search thing b/c i remembered this whole debate about matching RAM to get 128 bit versus 64 bit, and how much of a performance increase one gets w/ matched versus unmatched. Since most of the in depth discussion about it seemed to be from around the G5 intro date in 2004, the discussions seemed pretty inconclusive. Then there was this link which came to the conclusion that there was 0% speed increase from matched pairs in real world use. Of course that test only showed two 512s or one 1gb stick(s).

My debate is between getting another 512 (crucial says: US $72.99) or a 1gb (US $132.99). I can't imagine the boost between 1.5 gb and 2.0 being that big unless the matched memory benefit is really all that, so that's not much of a consideration).

So the question is, in the intervening time has the answer to this question been figured out? Considering the uses, will a 1 gb matched total give me great performance or will that extra 512 headroom above that (althogh 64 bit) really spell a detectable real world difference running multiple apps through two primary fast-user-switching users? Enough to justify $60 price difference?

Also, if you've got this computer, how much RAM do you have and how does it run for you?

And, of course, what about Tiger?

Thanks for any and all help.

[theapplegenius]

2GB is magic in two sticks. Don't skimp.

[icibaqu]

want to send me the extra cash? i'm also upgrading an iBook G4 at the same time.

[icibaqu]

for all those who take pleasure in viewing and not responding, i ended up ordering a single 1gb stick for a final total of 1.5 gb (as opposed to two matched 512s).

after reading threads on this board, appleinsider and macrumors the basic deal seemed to be that b/c matched sticks produce dual channel (instead of reading two seperate 64 bit busses, the computer treats it as one stick w/ 128 bit bus) that on the same amount of ram (i.e. 1gb stick versus matched 512mb) you allegedly get about a 10-15% performance increase w/ the matched pair. still, some say that you're really only seeing the benefit of 128 vs 64 if you're really pushing the ram, and it remains really unclear whether you actually detect the difference in the real world. also undetermined is the definition of "matched" - does the ram have to be installed at the same time, from the same manufacturer, etc. or does it just have to meet the same specifications. no one seems to know the answer to that one. last someone checked in all those threads, apple didn't say.

the difference between a 512 stick and a 1 gig stick on crucial, about $60 bucks. so w/ so many generally unanswered questions and no necessarily demonstrable gain from matching, i just said "**** it" and gave myself the extra headroom on top for a grand total of 1.5gb. also, if i had kept it at 1gb w/ matched 512's there is the possibility of my having decided 1gb wasn't enough and then i just bought a new stick for nothing. 2gb seems excessive for my needs at the moment.

the end
although maybe i'll say something about how much faster the computer is w/ the new stick that arrives in 5-7 business days. i know my fiancee will say something when we add a gig to her G4 ibook that's only got 256 w/ panther now. but that's another story.

[nascarnate326]

im a mac newb, so i didnt want to give advice on something i know jack about.

[lundy]

You did good.

Nobody can perceive a 10-15% performance increase anyway, even if it is manifest at the GUI. And as you say, memory bandwidth increases will only matter when running something that hammers the memory fetching in a non-cache-friendly (i.e. random access) way.