[rescue] SCSI CDROM and OBP2 (was Re: Sources of IRIX?)

Mike Spooner mike.spooner.ux at gmail.com
Fri Feb 10 05:39:34 CST 2017

> Date: Fri, 10 Feb 2017 00:12:07 +0200 (EET)
> From: Meelis Roos <mroos at linux.ee>
> To: The Rescue List <rescue at sunhelp.org>
> Subject: Re: [rescue] Sources of IRIX?
> Message-ID: <alpine.LRH.2.20.1702100009100.9866 at math.ut.ee>
> Content-Type: text/plain; charset=US-ASCII
> > The most important thing for using physical CDs is to have a CD-ROM
> > that supports 512 byte sectors or it won't work.  Plextor CD-ROM
> > drives support this and some Sun CD-ROM drives as well.
> Suns starting with some PROM version support switching the CD-ROM
> blocksize to 512 programmatically and these newer ones can use mostly
> any SCSI CD-ROM device.
> Does anyone know about SGI-s - can newer ones use any SCSI CD-ROM and do
> the sector size switch? If yes, which models need 2k sector CD-ROM and
> which models can take any?
> --
> Meelis Roos (mroos at linux.ee)
Sun OBP 2.7 and later can programatically switch *some* CDROM drives to
512-byte I/O blocksize - they issue a SCSI "Vendor-Specific Command" that
is understood by some Sony CDROM drives: the CDU-541/561/8012 in particular.

*Some* later OBP 2.* versions can also soft-switch some Sun-branded Toshiba
SCSI CDROM drives (XM4101) to 512-byte I/O blocksize, without having to
perform the (simple) trace-cut hardware hack. Note that this doesn't work
with IBM-branded XM4101 drives, which have IBM-specific firmware.

Mike Spooner

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