Re: GS/PC?

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

In article <DEzE5I.MKp@vaxxine.com>,
Michael Hackett <mhackett@vaxxine.com> wrote:
> 
> Don't the cards deal with the partition map, with the software then
> taking over to deal with each partition?  Or are the drivers decoding
> the partition map as well?

I don't know about the RamFast, but with an Apple SCSI card under
GS/OS, the GS/OS SCSI Manager bypasses the firmware on the card and
directly controls the hardware.  The partitioning mechanism is handled
by each driver (e.g. SCSIHD.DRIVER manages the partitions on a hard
drive, SCSICD.DRIVER does the same for a CD-ROM drive).

The drivers can only deal with Apple's partitioning scheme, which is
identical for Apple II and Mac hard drives.  Any non-Apple
partitioning scheme (e.g. the PC's partitioning scheme) will be
ignored, and the driver will treat the whole drive as a single
partition.  It would then be up to the FST to interpret the partition
map and provide several logical drives, but I don't think FSTs can do
this in GS/OS.

I expect the RamFast uses a similar scheme, but it combines everything
into a single driver.  The RamFast also only supports Apple's
partitioning scheme.

Under ProDOS-8, the SCSI card firmware deals with the partition map
(again, only supporting Apple's partitioning), and the operating
system sees a separate logical drive for each partition.

> The recent discussion about Zip drives on GEnie seems to point to the
> first case.  If you take a Zip disk that was formatted on a Mac (except,
> as has been discovered with FWB Toolkit (?), I believe), the RamFast
> will choke on it, while the Apple card has no problem with it.

I assume a ZIP drive is regarded as a SCSI hard drive (i.e. a "direct
access device" in the terms of the SCSI standard), as a SyQuest is,
for example.

I don't know why the RamFast would have trouble with it.  The RamFast
does make a minor change to Apple's partitioning, by making use of
unused space in physical block 0 (the driver descriptor map) to store
configuration parameters.  This shouldn't be critical to the RamFast's
operation, and should be ignored by a Mac or an Apple SCSI card.

Normal hard drives can be partitioned on a Mac or Apple SCSI card and
then used on a RamFast (or vice versa), as far as I know.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand