Because (from my understanding) the memory mapping is more complicated, when having pci slots.

Even for the Power Mac G4 systems it took an update to get all issues sorted out. With the Power Mac G5 is may be even more complicated as we deal with a different achitecture.

Geit

I gather that other Mac OSes address 4+ gigs of memory and still manage to do peripheral i/o only with mmu trickery...

well.. My g4 has 2gb ram and on bootup I have 1.42gb left. Hopefully the memory limit gets fixed on the G5.

Hmm... Forgot / didn't know 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.

(grumblegrumble stupid signed ints grumblegrumble)

[ Edited by ausPPC 30.05.2013 - 12:49 ]

I was wrong. My system has 1.5gb avail to it, 1.42gb free after booting MorphOS 3.2

as was told several times in past (also to me), limitation to 2 gigs are because of a/box, as AmigaOS uses 31 bit memory mapping (perhaps there aren't supported negative memory addresses, and the 1.5 gigs limit is because all devices (agp/pci/etc) requires also some plase to by accesible from a/box, and so another 0.5 gigs are disable for normal memory as it's used by pci etc... this is all the same for pegasos/powermac/minimac/powerbook/etc machines, and as now known, it's even worse with G5...

M.

> 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.

> Will this change with the next release or is this impossible?

"The limit will be gone with MorphOS 3.8."
https://morph.zone/modules/newbb_plus/viewtopic.php?topic_id=11069&forum=11&start=4