Re: SCSI Interface for A2GS

[dempson@actrix.gen.nz (David Empson)]

Geoff Pool <gepool@netway.com> wrote:

> I have a RamFast 3.01E and an Apple Hi Speed SCSI controller.  My questions
> are:
> 
> 1.  Is it possible to use an off the shelf SCSI CDROM drive to read ISO9660
> CDROMs using the RamFast and have a SCSI drive attached (mine is a Quantum
> LPS SCSI 1 drive) with ProDos paritions.  I know the Apple Hi Speed requires
> special, older types of CDROMS.

The Apple High-Speed SCSI card should work fine for accessing data CDs
with almost any modern CD-ROM drive, and with a large number of older
drives (as long as they comply with the standard command set).  Some
very early non-Apple CD-ROM drives won't work, because they used a
proprietary command set.

The specific problem with the Apple High-Speed SCSI card (and the
original Apple card) is audio CDs.  The SCSI card firmware and various
drivers only support Apple's proprietary audio CD command set, which
restricts you to three models of CD-ROM drive from Apple (the CD-SC,
CD-SC Plus and CD-150) if you want to play audio CDs under computer
control.  Apple switched to the SCSI-2 standard CD-ROM drive command set
from the CD-300 (2x external drive), and the Apple II SCSI card firmware
and GS/OS drivers were never updated to match this change.

The RamFast is generally a better solution for using a CD-ROM drive, as
it supports a wider range of drives for audio control.

You may run into compatibility problems with recent hard drives,
however.  Quantum Fireball models starting at about 500 MB don't work
with a RamFast, but do with an Apple SCSI card.  This may affect drives
from other manufacturers as well.

The cause: the RamFast doesn't implement the SCSI Arbitration protocol,
and doesn't have its own SCSI ID.  Some modern hard drives require these
features to be implemented by the host (and they are for the Apple
cards).

I don't know whether any recent CD-ROM drives are this fussy.