Mixing Ram


macrumors newbie
Original poster
Dec 31, 2002
Aurora, Ill
I just purchased a dual 1GHz PowerMac with 512 MB PC2700 Ram. I also just purchased another 512 MB stick of Crucial PC2700 Ram giving me 1 GB of Ram.

I have laying around a 256 MB stick of DDR PC2100 Ram. Can I add this 256 MB stick to my system?

Has anyone tried this before with success?

Just curious as to whether or not this would/could work.



macrumors 68020
Chances are - but i do not guarentee this - if you put in slower ram, all the ram will move that slow. At least, that is how my laptop ram works.

I am positive that if you put a PC133 and a PC100 stick in a powerbook, the ram will run at 100 and if one is 2-2-2 and another 2-3-3, it will run at the slower, 2-3-3 latency.

So, to make it short, it will work, it will just slow the system, i would sell the extra ram. you already have 1gb, 25% more might not make up for the slowdown in ram performance.

Sun Baked

macrumors G5
May 19, 2002
Re: Mixing Ram

Originally posted by mbutlerdelrio
I have laying around a 256 MB stick of DDR PC2100 Ram. Can I add this 256 MB stick to my system?
NO, the 1 GHz Mac is running a 167 MHz bus, and the DDR memory is the 333 MHz variety (ie PC2700 Ram).

The 867 MHz machine runs a 133 MHz bus and uses PC2100 DDR Ram @ 266 MHz.

You can use the faster RAM is the slower machine, but not the slower RAM in the faster machine.

Must meet the minumum standards dude.

[edit - It's just a guess, and a gassy opinion ;) ]


macrumors 6502a
Aug 5, 2002
Notre Dame
i know this question may be a little redundant, but i just want to make sure. i bought a 256MB pc133 stick to throw into my17" iMac. the ram i have in there now is pc100, so the faster ram i'm putting in should work just fine, right?


macrumors 601
Jan 14, 2002
South Dakota, USA
Yes PC133 works fine in a computer that was designed for PC100. I bought a PC133 256MB stick for dirt cheap at Best Buy and plugged it into my iMac DV 400 and left in one of my old 64MB PC100 and all 320MB shows up and works great. The only thing is there is not performance increase, it just runs the PC133 at PC100 speed. Works just fine. I have no idea about the DDR ram however, but I would assume it is the same...that means it is backwards compatible, but not forwards compatible.
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