[wpd7]

Apple's website shows that you can add up to 4GB to the iMac, but can only address 3GB. Is this a limitation similar to Windows XP where it can only address 3GB due to the OS? When and if I do upgrade to Leopard/Vista on Bootcamp, will I be able to address all of the 4GB? it is noted that the system profiler sees all 4GB, so I know its not a hardware limitation.

From Apple:
"Note: If you do install a 2 GB SO-DIMM in both the bottom and top memory slots of the computer, the About This Mac window and Apple System Profiler will both show that you have 4 GB of SDRAM installed. However, Activity Monitor and other similar applications will reveal that only 3 GB of SDRAM has been addressed for use by the computer."

Now for a bonus question- I want to install a 750GB HDD in there. I know how to do it, but do I have to have the Genius Bar people or an Apple certified tech to do it to keep my warranty intact?

[pheonixash]

The 3 GB is due to a chipset limitation. Intel's chipset can't address more than 3.25 (roughly) GB of RAM. This was to be fixed with Santa Rosa, which Apple hasn't yet adopted for the iMac. The new MBP's can address all 4 GBs of RAM.

And yes, you will need an Apple Certified Tech to make that modification to keep your warranty intact.

[Eug]

Has anyone tried 2x2 in the iMac yet? Do you get dual-channel speed with 3.25 GB, or do you get single-channel speed with 3 GB?

[wpd7]

pheonixash- so would you recommend a config of 1GB + 2GB or 2x 2GB, will dual channel still work even if the chipset cannot address it all and will it be worthwhile over the cost? =)