> Hmm, what, apart from an eventual BSD disklabel would you want to write
> into the first 16 sectors (assuming you meant sectors above) of the CD?

 The "El Torito" stuff must be written somewhere, no?

> In ISO9660, these are free, and El Torito doesn't use them either (well,
> actually you may use this space for El Torito information, as well as you
> may use it for e.g. Rock Ridge information, but both can be anywhere on disk).

 Anywere? I doubt that the standard BIOS of a PC is able to seek the 
"El Torito" information just anywhere on the CD.

> One way is to include a floppy image on the disk and point an El Torito
> record to it.  The BIOS recognizes this and sets things up so that it
> looks to the machine as though drive A: now contains exactly this disk
> image (yes, there is support for 1.2M, 1.44M and 2.88M disk images).
> Your real A: drive becomes B: and your real B: drive is lost.

 This is the standard way, and it works almost everywhere.
Officially, at least last time I read the specifiations, you can even
choose between different images during bot time.

> You can also have a hard disk image of an LBA addressable disk on it.
> This will become your C: drive (BIOS drive number 80), and all other
> drives will accordingly be incremented, i.e. C: becomes D: etc.

 This option does not seem to work everywhere. I have tried this on
several occasions and failed. The image was not recognized or been reported
as "non bootable".

> And you can simply boot a memory image from the CDROM into memory and
> just run that.

 Oh? This sounds very interesting.

> Of course, mkisofs doesn't support these latter options (or so I
> understand).

 It doesnt.

> Also note that I have to admit that I too only used the first option
> myself to make bootable CDs.

 Which usually is all you need to install NetBSD.

-- 
Markus Illenseer