Hello,

> The IPL levels are a purely OS and even port specific entity.
Ok, first I thought there's a connection or at least a similarity to 68k-style interrupt levels. Silly me :)

> I can already
> point to another example of where this is going to cause problems - the
> second mediabay on Wallstreet Powerbooks. This is because the I/O
> controller for that bay is the one possessing the irq, and the disk drive
> and IR device have to share it. I don't think it is reasonable to have
> expectations that in the future there will be less sharing of irqs; quite
> the opposite, I would think, as some Macs are quite crowded.
Yeah, I only need to look at my iBook G4 - about twice as many IRQ sources as the S900 but they're hardly shared. On the other hand PCs would need to do a lot of sharing, with only 16 hardware IRQs ( ok, 24 in some ) and more than half of them hard-wired. I think I need to find a way to get around the whole 2nd PCI bus in the S900 sharing the same IRQ - it works, sort of, but it doesn't seem right.

have fun
Michael