Re: SCSI-IDE-CF Experiment

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

pitz <pitz.wong@gmail.com> wrote:

> I was testing a SCSI-IDE-CompactFlash setup for a different platform a
> few weeks back.  On a whim, I thought I'd bring out the Apple High
> Speed SCSI card to test a similar setup on a IIgs.  I used a SCSI-IDE
> adapter, a cheap IDE-CF adapter, and a regular 128MB CF card.
> 
> http://picasaweb.google.com/simplepractices/Posts#5229593535780726082
> 
> System 6.0.1 boots fine from the first partition in my CF card -- this
> was the same CF card taken from a working CFFA setup.  It will not see
> the other partitions in the CF card, since I think SCSI and IDE
> partitions are set up differently.  And I didn't want to re-format my
> CF card because I still use it with my CFFA.

The issue isn't "SCSI vs IDE" partitioning, rather "Apple vs CFFA
partitioning".

The Apple SCSI cards expect to find a standard Apple partition table
(used by Apple's SCSI cards for the Apple II, all Macs with SCSI or IDE
from the Mac Plus up to the last PowerPC model, and still supported by
Intel Macs).

The CFFA doesn't have a partition table at all. It uses a "hard
partitioning" scheme where the settings on the card define the
partitioning rather than having a dynamic partition table which is
stored on the card.

This is a somewhat unfortunate design, because it means the CFFA
partition scheme is not compatible with anything else (unless the other
device also supports a hard partitioning scheme and can be configured to
the same pattern of partition sizes). Supporting a dynamic partition
table would require a moderate amount of RAM on the card, but it could
be supported by a GS/OS driver of the CFFA as long as you didn't need to
boot from the card.

In your test configuration (SCSI-IDE-CF), the SCSI card is seeing a
device with no partition table, so it assumes it is a single volume,
with size equal to the total size of the CF card.

ProDOS sees a huge volume but is limited to 32 MB, and the existing file
system on the card (starting at block 0) is valid, so it works as
expected, but cannot access the later "partitions". If you reformatted
it as ProDOS, it would set up a 32 MB volume and ignore the rest. If you
reformatted it as HFS, it would be a single volume occupying the entire
CF card.

-- 
David Empson
dempson@actrix.gen.nz