Subject: Re: Bootable CDs
To: None <simonb@NetBSD.ORG>
From: Ross Harvey <>
List: port-pmax
Date: 09/17/1999 22:27:15
> From: Simon Burge <simonb@NetBSD.ORG>
> Simon Burge wrote:
> > From the looks of things, alpha needs the last 32 bytes of the first
> > sector (with a valid checksum).  I think the pmax needs 24 bytes
> > starting at byte 8 - the rest of the first sector doesn't matter.  You
> > mention sparc as a sector-0 dependant arch - do you know what it needs
> > and if there are any others that need sector zero?
> Thinking about this a little more - at the moment the pmax stuff assumes
> that the first stage is in the remainder of the the first 8kBytes of
> the disk, and it looks like the Alpha does too.  One idea that comes to
> mind it to allow installboot to take an offset into the disk where stage
> one is located.  Then on a CD, you could have the iso9660 filesystem
> finishing at some certain offset before the end of the CD and either the
> pmax or alpha stage one (or possible both if some other architectures
> want stuff in the first 8 sectors) after the iso9660 filesystem.
> Thoughts and ideas?

Sounds like you are almost there, actually. Regarding pmax vs sparc vs
alpha, I've already got alpha and sparc booting from the same sector 0;
pmax would be easy to add. (A whole lot easier than sparc+alpha was, BTW.
It doesn't overlay and IIRC it does not have a checksum.)

And yes, one or the other is going to have to put the first stage boot out
of the way.

iso9660 does not fragment files, so the first stage program could be a
named file on the disk, if the installer prog understood that.  Also, the
iso9660 FS starts about twice as far away from sector 0 as FFS does, so
there is probably room for both first stage programs anyway.