Re: SCSI-IDE-CF Experiment

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

"Henry S. Courbis" <apl2research(a.t.)comcast.net> wrote:

> pitz <pitz.wong@gmail.com> wrote:
> > Having said that, the SCSI-PCMCIA setup you mentioned should present
> > itself as a regular SCSI block device, and the GS/OS SCSI driver
> > should be the only additional software you need.
> 
> I see.  What's the advantage to using the GS/OS Driver as opposed to just
> loading GS/OS on the CF Card without the Driver?  I assume more then 4
> Volumes would then be supported?

To use an Apple SCSI card with GS/OS you must have the SCSI drivers
installed. Without the drivers, GS/OS complains at startup and only
gives access to the boot volume (first partition on device with highest
SCSI ID).

In a more general case of an third party disk interface card of some
kind, GS/OS prefers to use a native driver if one is available, but it
will revert to using a "generated" driver that is able to call the
firmware on the card (for a Smartport driver or ProDOS block driver in
the firmware).

The main advantages of a native driver are signficantly better
performance, and more volumes per slot.

> Well, as mentioned above I now have a fully working setup.  I have tired it
> with the Apple II SCSI Card and the Apple II High Speed SCSI Card.  For some
> reason the unit only seems to work with the Apple II High Speed SCSI Card,
> with or without Active Termination.  It should be noted that both cards have
> the Termination Power mod and the Drive does seem to require it.  Any ideas
> why one SCSI card would work and the other does not?  The IIgs just seems to
> hang when trying to access the Drive with the Apple II SCSI Card.  No issues
> at all with the Apple II High Speed SCSI Card.  My test SCSI HDD works just
> find with both Controllers too.

The Apple High Speed SCSI card is a newer design and may have better
compatibility with later implementations or more features of the SCSI
standard, though with GS/OS I'd expect that the differences between the
cards would only affect the electrical characteristics of the hardware
interface and the transfer speed (the software implementation of the
SCSI protocol is being done by the same GS/OS driver for both cards).

Your SCSI-IDE device may be timing out a transaction because the
original Apple SCSI card is simply too slow. (If so, that is a design
flaw.)

-- 
David Empson
dempson@actrix.gen.nz