Apparently September '06 iMacs will take up to 2Gb SODIMMs in their 2 memory slots, but will perform better with matched pairs, but have a maximum of 3Gb
. ... 3? 3Gb? Um, why? ... and the max. memory configuration is not the performance-optimized one? Urr? So, you can have maximum memory with 1x1Gb + 1x2Gb, or maximum performance of memory with 2x1Gb.
Luckily, my iMac is not encumbered with such odd capacities, as it will only take up to 2Gb (ok, so that's not really better at all :) and will perform better with matched pairs of SODIMMs, so 2x1Gb is the ideal configuration for it.
I didn't know about the performance optimization with matched SODIMM pairs until this morning. I just bought 1x1Gb SODIMM to put in my 512Mb-equipped Jan '06 iMac (1x512Mb, I think/hope--yes, they shipped at least some without the optimal configuration for performance). I think I'll be ok with 1.5Gb of memory at not entirely optimized performance rather than 512Mb and massive swapping. :)