On the main board, and not just the old ones. These days it's
typically in the chipset's south bridge. "Third-party DMA" is
sometimes called "fly-by DMA". The ISA card is a slave, as is memory,
and the DMA chip reads from one ands writes to the other.
IDE didn't originally use DMA at all (but floppies did), just
programmed IO. These days, PC chipsets mostly have some form of
extended higher-performance DMA facilities for stuff like IDE, but
I'm not really familiar with the details.
<aside>I do wish Linux didn't have so much PC legacy sh^Htuff
embedded into the i386 architecture.</aside>
> > There was also a 24-bit address limitation.
>
>Yes, that's in the number of address lines going to the isa card.
>We work around that one by having an iommu arena from 8M to 16M
>and forcing all ISA traffic to go through there.
-- /Jonathan Lundell. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/