Re: SCSI Partition question

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

In article <20167YNIMVOOIGANWYS@ods.sol.net>,  <dreamer@ods.sol.net> wrote:
> 
> I recently acquired a 300Mb CDC hd for my BBS.  In attempting to
> partition/format it, I discovered, much to my dismay, that I could only
> make 7 partitions at 32767.5k per, for a total of about 229Mb.  This was
> a bit confusing, as I thought ProDOS 2.0.x could handle up to 8
> partitions, not 7.  I went on to discover that ProDOS can handle up to 7
> partitions at a time and a total of 12 devices.

I wasn't aware that there was a fixed limit.  ProDOS-8 cannot handle
more than 14 block devices, so after counting any RAM disks (including
the standard /RAM volume in auxiliary memory), 5.25" drives (2 per
controller, even if you only have one drive), 3.5" drives, etc., the
remaining number of available units should be the number of partitions
you can have.

I think the ProDOS-8 2.0.x remapping of partitions to unused units
will skip the second unit for a slot which has a single device (e.g. a
SuperDrive controller with a single drive connected).  For some reason
my second and third hard drives don't want to come online just now, so
I can't check this.

> It also doesn't matter if the partitions are all on one HD or on
> several.  It will still only recognize the first 7.  I believe I used
> a program called SCSI Hard Drive Utilities V0.98 to partition/format
> the drive. 

I've never heard of this software.  What SCSI card are you using?

The original Apple SCSI card supports a limited number of partitions -
7 per drive, according to the technical reference manual.  Further
information in the manual implies that it only supports 7 partitions
in total.

The Apple High-speed SCSI card supports up to 111 partitions, spread
over as many drives as required.  You wouldn't be able to access them
all from ProDOS-8, of course.

I don't know what limit the RAMFast card has.

> Does anyone know what the access speed of this HD is as it seems MUCH
> slower than either of my two previous HDs (A Seagate ST296N and a
> Quantum P80S inside a Digicard case)?

It could be a problem with the interleave - if the drive was formatted
with a bad interleave factor (e.g. 10:1, which is used by the Apple
HDSCPARTITION utility), the drive will have a slower transfer rate.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand