To optimize performance, install matched pairs of DDR SDRAM DIMMS. For example, install 2-512M RAM modules instead of 1-1G module. Why? Because your memory bus works at 128-bit width with matched pairs of DIMMs. This can give you up to 30% better performance for some opperations.

UPDATE: According to Barefeats.com, "THE REAL WORLD VERDICT: AVERAGING 8 TESTS, NETS 0% GAIN FROM MATCHED PAIRS."

Read about it here:

http://www.barefeats.com/imacg5d.html

Also set the CPU to highest found in Powersaving
prefrences.

This will also make your iMac G5 a bit more lively

Will having two DIMMS that aren't made by the same company (ie. 1 Crucial and 1 Kingston), but have the same CAS latency and such, still run in 'dual channel' 128-bit mode?

Absolutely. I have RAM from Apple, OWC and Crucial in mine.

You have 3GB of RAM and it's running dual channel? WOO!

Newegg is out of the RAM that I ordered for my iMac a couple of weeks ago, so i'm going with a different brand. Right now, i've got one 512 and one 256 in the iMac, so i'm wondering if taking the 256 out and putting a 512 will really give me an increase in performance (as well as setting the memory channel to 128 bit.)

I got the mac on Jan 5th and I've been going on a shopping spree. Can you recommend anything good to clean the screen with? I read not to use chemicals, but eh... the screen is just so gorgeous.

I'm on a PowerMac.




To be honest with you, I don't think you will notice that big of difference going from 768 to 1G - even at 128-bit. I would suggest replacing the 256M module with a 1G module.

Yeah, I was thinking about replacing the 256 MB with a 1 GB... but then i won't be 128 bit unless i get another 1GB.

Thanks for your help though!

Read this:

http://www.barefeats.com/imacg5d.html

Apparently, matched pairs don't make a difference in "real world" computing.

Does it matter what voltage rating the RAM is (ie. 2.5 & 2.6)?

Thanks in advance!

Most overlooked factor: The RAM must be compatible with bus slewing, otherwise you're nailed to leaving your system at Highest setting versus Automatic.

"bus slewing"?

Details on the various modes are provided in Apple's Developer Documentation.

To lower power consumption, heat generation, and fan noise, the Power Mac G5 computer incorporates an automatic power management technique called bus slewing. Bus slewing is designed to run at high processor and bus speeds and high voltage when the demand on the processor is high, and to run at low processor and bus speeds and low voltage when the demand on the processor is low.

http://developer.apple.com/documentation/Hardware/Developer_Notes/Macintosh_CPUs-G5/PowerMacG5/1Overview/chapter_2_section_5.html


Don