> g4 powermacs also have a 1.5GB limit in OS 9 - and max out at 2GB.
> But don't know if that's a hardware of software limitation.

The 1.5 GiB limit in MacOS9 is a software limitation, whereas the 2 GiB limit of the AGP Graphics, Gigabit Ethernet and MMD models as well as the 1.5 GiB limit of the Digital Audio and Quicksilver models are hardware limitations.