Subject: Re: Boot from CD-ROM
To: None <markus@TechFak.Uni-Bielefeld.DE>
From: Terry Moore <tmm@databook.com>
List: current-users
Date: 04/14/1995 15:17:04
 
> > I've never seen an i386 type box booted off a CD, not to say that it can't
> > be done, just that the way CD-Rom drives are installed on Intel boxes
> > doesn't lend itself to this sort of thing.
> 
>  How do you start NetBSD on i386? With a Bootmanager or with a tool started 
> under, say MS-Dog?

When booting a CD-ROM, you need BIOS support.  Phoenix Technologies has
been promoting a BIOS / CD-ROM bootability hack which involves putting
a diskette image (FAT filesystem) onto the CD-ROM, which can be booted
in the normal way by DOS (standard DOS is quite inflexible in its boot
requirements).  This could be used, of course, by anybody as a transition;
put a diskette boot block in the CD-ROM that uses INT 13 to load the 
reset of the image, etc.  However, this won't be univerally available
because it requires a BIOS change, and also required Enhanced IDE
support (with the CD-ROM on the enhanced IDE port).  I reckon that
it will be about another year before booting from CD-ROM becomes an
easy-to-contemplate option in the 386 world.  On the other hand, 
every x86 comes with DOS; which means that it's really very easy to
put a bootstrap program on the CD that will launch the install process
from a DOS prompt.

At present for NetBSD/i386, you start (from zero) with a boot diskette
generated using tools supplied on the CD-ROM.  After installation is complete,
NetBSD uses the standard IBM BIOS procedures to bootstrap.  

>  Hell, my CD is (almost) for Amiga-only :-) All I want to do is to be able to 
> boot from CD. This cant be done because obviously the kernel seeks for UFS and
> most probably doesnt even want UFS which uses 2048Bytes blocks than standard 
> 512.

Of course, you can always hack the CD driver to simulate 512 byte blocks
by reading the 2K physical block into a driver buffer, then delivering the
512-byte chunk requested to the caller.  Any performance hit will be
swamped by the slow access time of the CD anyway.

--Terry