I was looking for something else, and I randomly bumped into this article... http://docs.info.apple.com/article.html?artnum=300082 I am familiar with the idea that some PowerMacs benefit from matching memory module configurations in terms of memory bus rates, but I had not bothered to be aware of this for my iMac, since I've been very happy with it overall... However, now I wonder if there might be an appreciable benefit in doing an upgrade, as my iMac gets older. It is: iMac G5 (Ambient Light Sensor), i.e. Rev. B 2.0 GHz / 160GB HD (7200RPM) 1.5GB RAM (i.e. 1x1GB and 1x512MB PC3200 modules) Notably, I consistently get zero or nearly zero pageouts, meaning I probably will not benefit from having 2GB in and of itself. Upgrading this Mac to 2GB would only cost $60, but it would only be beneficial at this point in terms of anything I would get speedwise out of the 128 bit memory bus. Has anyone done this on an ALS or Rev. A iMac? Did they consider it worthwhile? Does anyone know of benchmark data (I didn't see any in some Google searching)? It might not be bad to do at some point for me, purely from the perspective that there's some chance I will get Leopard for this Mac. But then, $60 is $60.... Thanks for your input!