On Tue, Feb 04, 2003 at 12:56:18PM +0000, David Laight wrote:
> On Tue, Feb 04, 2003 at 01:09:16PM +0100, Rumi Szabolcs wrote:
> > Hello!
> > 
> > I am trying to find out what is needed to support >128GB disks
> > on i386pc. AFAIK 1.6 does have IDE 48-bit addressing support,
> > please correct me when I'm wrong. But it also needs some kind
> > of motherboard level support, isn't it?
> 
> It shouldn't require motherboard support.  The is a possibility
> that the BIOS might get confused (probably only about the disk
> size), but that would only make it difficult to boot from such a disk.
> 
> IIRC the 48bit sector support is done by having a two entry fifo
> on each of the sector number registers, and using a different
> command to do the actual read and write.  All this happens
> down on the disk, not in the PCI (or whatever) card.

Well, most pci controllers do some kind of buffering between the
CPU and disk, and sometime do some smart stuffs (like snooping the
commands, to automatically adjust to the DMA mode in use).

A too smart, but too old controller may choke on the double-write on
the registers.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 24 ans d'experience feront toujours la difference
--