I have x86 Ubuntu but that self-evidently can't address all 4GB RAM. One site suggested that enabling PAE was as simple as installing the linux-server kernel and the linux-headers-server and then installing the driver from Nvidia (7600GST). If only it were that simple. I haven't made it to the last part yet because my computer keeps freezing at "loading hardware drivers". From what I have been able to infer, the freeze invariably occurs at the stage where the video card gets into the picture. Pte errors, bad swap allocation, .. - all directly related to memory management (RAM is fine, though, I used memtest86+ and none of my other systems are having issues).

I went into BIOS and disabled memory mapping. This time the system did boot properly but it also meant that I couldn't t access more than 3GB of my RAM. That's no better than using the generic kernel with memory mapping disabled. Not to mention the huge inconvenience of having to go into BIOS every time I switch between Ubuntu and a 64 bit system.

I have also tried various boot arguments (pci=nommconf, mem=6G, agp=off, irqpoll, ...) but nothing seems to work. Switching to the vesa driver doesn't help either.

For what it's worth, my system is:
Core 2 Duo 6600
4x1GB Corsair PC6400
Nvidia 7600GST
ASUS P5B

Has anyone been able to use PAE with Ubuntu? Thanks in advance for any suggestions.