[rescue] SCSI DVD drives

Charles Shannon Hendrix shannon at widomaker.com
Wed Jul 11 13:51:43 CDT 2007

On Wed, 11 Jul 2007 11:44:02 +0100
Peter Corlett <abuse at cabal.org.uk> wrote:

> On Wed, Jul 11, 2007 at 12:26:37PM +0200, Clemson, Chris wrote:
> [...]
> > Well true, that would be simplest option - in fact I bought a SATA DVDRW
> > drive and controller, but adding any more I/O cards results in not being
> > able to boot off my SCSI card, which is a shame.
> *This* is one of those really nasty corners of the misdesigned PC boot
> process, and affects my Frankencomputer that I fortunately don't use all
> that often. IIRC, PC BIOS only seems to allow for an IDE and a SCSI disk
> controller. Since the motherboard already has IDE, add-in cards have to
> fight to be SCSI. That the add-in card is actually IDE is moot, it pretends
> to be SCSI so that it is bootable.

This actually depends on your controllers, their BIOS, and your PC BIOS.

If all of the parts are truly PCI compliant, they should negotiate for their
slice of the IRQ, DMA, and boot vector pie and BIOS should see all of them.

Some controllers assume they are "THE" controller, but that's really a
violation of the specs (such as they are).  Some BIOS also don't do this

My Asus A8N5X has no concept of ATA versus SCSI at all.  It initializes all
(compliant) controllers and can see all of their drives, let you pick their
boot order, and individually boot any of them at startup by hitting F8 and
picking from a menu.

It has one of the better, more compliant BIOS that I've seen in awhile.

I still find PC BIOS maddening, but truthfully... a lot of the UNIX ROMs
aren't that great either.

I think all of it could use a lot of improvement.

shannon           | An Irishman is never drunk as long as he can hold onto 
                  | one blade of grass and not fall off the face of the earth.

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