IRQS on 6 Slot Macs

Geert Uytterhoeven geert at
Wed Nov 5 09:30:06 EST 2003

On Tue, 4 Nov 2003, Jeff Walther wrote:
> At 20:14 +1100 11/04/2003, Benjamin Herrenschmidt wrote:
> >>  After all, one can, in theory, add 1024 PCI slots to a machine using
> >>  PPBs.   There aren't going to be 1024 interrupts available.
> >
> >Why ? Some iSeries have up to 2048 irq lines afaik ;)
> By iSeries, do you mean iBook and iMac?   Or is that something else?

iSeries are the big IBM boxes formerly known as AS/400.

> I think I can find GC's connection to MESH as well, but I'm
> uncertain.   I believe that MESH is just a licensed NEC (now LSI
> Logic) 53CF96 and I have the pinout for the 53CF96 so tracing

NCR, I assume?

> I haven't dug into that, but I'd like to know how they made that
> work.  Does an Enet card require an interrupt?  Does it ever master
> the PCI bus?

Ethernet prefers to have an interrupt, else it becomes quite slow :-)
Most modern Ethernet interfaces do bus mastering. Old NE2000 clones don't.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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