Subject: Re: pciide, DMA, and the alpha...
To: Jason Thorpe <firstname.lastname@example.org>
From: Chris G. Demetriou <email@example.com>
Date: 08/11/1999 20:22:51
Jason Thorpe <firstname.lastname@example.org> writes:
> On the PC (and on some older Alpha models, specifically 21064+APECS and
> some LCA models), PCI interrupts are routed through the ISA PIC(s). These
> interrupt controllers have 8 interrupt lines each. There are two such
> controllers, and you end up with 15 interrupt lines (I think :-) after all
> is said and done.
This is too generous for most boards:
the routing is typically programmable in software (it is on most PCs
that i'm familiar with -- new ones might fix it, and on those alpha
models), and there are only four registers which can be
programmed... leading to all PCI interrupts being routed through no
more than 4 or so ISA IRQs... "lose."
Chris Demetriou - email@example.com - http://www.netbsd.org/People/Pages/cgd.html
Disclaimer: Not speaking for NetBSD, just expressing my own opinion.