22 Nov
2005
22 Nov
'05
12:33 p.m.
Tony Duell wrote:
Julese Richardson seems to think there'll be a problem with the fact that
the Filestore will want a deive that suports 256 byte sectors.
Of course with ST506/412 you're probably OK - the Adaptec board probably
supports various sector sizes (and of course the drive is non-intelligent and
won't care). The only manual I have to hand is for the OMTI board, but that
certainly supports 128/256/512/1024 bytes/sector.
But with SCSI straight to the host adapter it'll be somewhat different and the
drive needs to support whatever the initiator requests, which I expect is 256
bytes/sector. Acorn *might* have moved things along by then and be doing 512
bytes/sector - although in all fairness 256 is likely more suitable for the
nature of the data stored on a typical fileserver.
Pete, were there two releases of the format utility - one for ST-type disks
and one for SCSI? Strictly speaking in SCSI-world there's no need to define
drive geometry as it can be queried from the target drive itself, but this
would be a necessary step when using an ST-type drive. (of course ST-type
drives also need geometry subsequently stored - presumably in block 0 - which
isn't necessary for SCSI)
Certainly prior to formatting an ST-type disk with the OMTI board you need to
issue an 0xC2 "assign disk parameters" command to tell the board what it's
connected to; I can't imagine this is different with the Adaptec (unless it
does it via a vendor unique extension instead). I *think* this would all be
unnecessary for SCSI, although I suppose it might be possible to assign
different geometry to the SCSI drive that its physical geometry (providing you
don't exceed total space available) and the drive would translate accordingly.
Following that it's just a case of issuing a 'format unit' command (and
subsequent verification) to either the Adaptec board or in the case of SCSI
direct to the drive.
So there are a lot of similarities in the process, but there's an extra step
for ST-type drives that isn't (strictly?) necessary for SCSI.
True, Imagedisk is probably a more viable format these days (hat off to Dave
D). I've just gained another PC, so time to see if that one supports FM
recording on the disk interface (if not it goes in the bin - I don't need more
hardware around here :)
I'm sure It'll turn up sometime. I don't know what it is about Acorn, but
their stuff seems to vanish for years and then suddenly appear again. I bet
it's lurking in someone's garage somewhere...
The E20 hard disk unit contains the standard Host
Adapter card linked
to
a 20NByte SCSI hard disk. That was the normal
thing to link to the 34
pin
connector on the E01. It sohuld be relatively
easy to put one of
those
together... Is there any restriction on the hard
disk size? What
would
happen if I linked up a unit of several hundred
Mbyte capacity? Would
it
just not work, would it only see it as a 20Mhyte
unit, or would it
see
the whole thing?
There will be some limit,
but I'm not sure what it is. More than 20MB,
for sure. Might be 500MB, maybe less. I know that stacking filestores
use the same code, and I know that although the largest ones sold and
supported by Acorn were 60MB, they had bigger in-house. making a
teledisk image; that *might* work. They're double-density,
256 bytes/sector, 16 sectors/track.
Should be possible, but not a lot of use to me as I don;t haev Teledisk
(and don't intend to try to write soemthing to handle its images). I
might have a go at writing programs to handle Imagedisk stuff though. Ditto! The
test box pre-dates the Master series, though. It was
around when Beebs were.
It's a pitty the software seems to be long-lost.... >> The chap who sold this to me included a couple
of such Sony
>> drives, alas missing the front panels and eject buttons.
I'm sure I can rustle up a pair of suitable drives through the museum if you
have no luck (I've been deliberately rescuing 5.25" drives from landfill, but
it's probably time to start doing the same with 3.5"...)
cheers
Jules