Yeah, you're right, they wanted 512 instead of 2048 bytes per sector to use the CD as a HD. But I think that at least one of the Unix vendors shipped the install media as 520 byte sectors, with 512 bytes of data and 8 bytes of checksum. In order to duplicate the discs, you needed to own a writer that was fancier than average (i.e. a SCSI unit, not an IDE one).
I keep a DEC RRD-40 drive (with its weird pre-caddy disc holder thing) around for the purpose of booting old DECstations. Not sure if it used 520B sectors though. I think I have the manual .. somewhere.
