Why don't third-party CD-ROMS work on my sun?

Why don't third-party CD-ROMS work on my sun?

When Sun first decided to add CD-ROM support, there were already a great
number of systems in the field, all of which contained boot proms that
expected to boot from disks with 512 byte sectors. Sun had to decide
between replacing a whole lot of boot proms or finding a way to make a
CDROM act like a disk with 512 byte sectors in order to support it as a
boot device. They chose the latter approach.

Many third party CD-ROM drives use 1024 or 2048-byte sectors, which causes
the SCSI driver to see a "data overrun". When the driver asks for N
"blocks" (which it thinks are 512 bytes each ) it gets more data back than
it expected.

Some CD-ROM drives can be told to use 512 byte sectors by setting a jumper,
cutting a trace, or using a software command (mode select). Details vary
widely, but if you are seeing a data overrun on a third party CD-ROM, then
it is most likely doing 1K or 2K transfers and will need some work to be a
boot device for a Sun.

Thanks to Kevin Sheehan

For more information about third-party CD-ROMS on Suns, consult the
CD-ROM FAQ, maintained by Mike Frisch and
Martin Hargreaves . It can be found on the
World Wide Web at "http://saturn.tlug.org/suncdfaq". A UK mirror is
available at "http://www.datamodl.demon.co.uk/suncd/".


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