Re: SCSI <--> CF/SD Reader

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

Steven Hirsch <snhirsch@gmail.com> wrote:

> On 06/30/2011 01:49 PM, pitz wrote:
> > On Monday, June 27, 2011 6:44:19 PM UTC-7, Steven Hirsch wrote:
> >> Amiga hard-disk prep has options for LUNs, but that's about the only
> >> place I've seen it.
> >>
> > Most Unix systems understand multiple LUNs.  I've worked with some before
> > that addresses them like sd(x,y,z), x being the target SCSI ID, y being the
> > LUN, and z being the disk slice/partition.
> 
> My comment was restricted to the realm of classic computing.  If any of the
> Apple SCSI cards understand LUNs, it's news to me.  But, the older I get the
> more things do become news...

That tickled something in the back of my brain.

In article <1d6j1wf.1fg67v7udtwmuN@dempson.actrix.gen.nz>, posted Fri,
27 Mar 1998 03:00:51 +1200, subject "Commodore drives can be controlled
on Apple II serial!", David Empson <dempson@actrix.gen.nz> wrote:

> David Wilson <david@uow.edu.au> wrote:
> 
> > This card is not a SCSI card for the Apple but a SCSI target to connect to
> > your existing SCSI bus (and existing controller card). The disks attached to
> > the card would appear to be SCSI disks as far as the Apple was concerned
> > (although with more than one disk it would probably need to use SCSI LUNs
> > which may or may not work with existing SCSI cards on the Apple //).
> 
> They are supported by the Apple HS SCSI card firmware (at least the
> documentation says they are - I've never encountered a device that uses
> LUNs, so I haven't tried it), but I don't know about the original Apple
> card or the GS/OS drivers.
> 
> I would be surprised if the RamFast supports them, but this could be
> fixed with a firmware upgrade.

I don't have any more information to add at this point, and haven't
re-read the HS SCSI documentation, but it seems that at least the HS
SCSI firmware does support LUNs, and it would be logical to assume that
the GS/OS drivers should as well (which would also work with an original
Apple SCSI card).

The original Apple SCSI card firmware is not likely to support LUNs,
because it can only mount a total of seven volumes (e.g. one partition
per drive, or several partitions on fewer than seven drives).

The HS SCSI card firmware can mount about 110 volumes. Allowing for
seven SCSI IDs, that limit could only be reached with single-LUN devices
if they had an average of 15 partitions each, which seems unlikely. LUN
support is the most likely explanation for that limit.

GS/OS drivers can mount a maximum of 63 volumes per driver (e.g. 63
Apple SCSI hard drive partitions plus 63 CD-ROM partitions), over all
SCSI cards installed in the computer. Given the possibility of multiple
cards, and the 63 merely being a general implementation limit of GS/OS,
this brings the numbers down enough that LUN support isn't certain.

I don't know about the RamFast (or its GS/OS drivers).

-- 
David Empson
dempson@actrix.gen.nz