--- Joe <rigdonj_at_cfl.rr.com> wrote:
> At 09:12 PM 7/22/02 -0700, you wrote:
> >
> >--- Joe <rigdonj_at_cfl.rr.com> wrote:
> >> At 06:26 PM 7/22/02 -0700, Ethan wrote:
> >> >--- Don Maslin <donm_at_cts.com> wrote:
> >> >> ...I see no reason why a regular SCSI
> >> >> drive could not be installed in lieu of the ACB-4070 and ST-411/506
> >> >> interface drive.
> >> so the host has to "know" the geometry,
> >>
> >> Hmmm. But how do you tell it the geometry?
> >
> >That entirely depends on the software/firmware on the host.
>
> This is on a CPM machine so the program isn't that fancy. But I was
> reading through the manual again last night and it says that the source
> code for the HD install program was included so that you could modify it
> for the particular drive. I don't have that file with my stuff so I'll
> have to search for it.
That would be essential I would think. Almost certainly, the expected
drive geometry is embedded in the partitioning software which may or
may not be tightly coupled with the low-level formatting software you
reference above. With source code, you could turn off any features
you don't want, and change the tables as needed (although you *could*
just ignore the rest of the drive and only use the first few megs; unlike
an ST506/ST412/ESDI/SMD drive, modern SCSI and IDE drives present a
virtual model of tracks and sectors because they have a variable number
of sectors per track and you can't easily *know* what physical cylinder
you are on).
In a similar vein, between myself and some folks in Michigan, Finland
and Germany, we've managed to tweak the partition tables for a Commodore
D9090 disk drive which happens to have an OMTI SASI<->ST506 bridge
controller so that it can use other drives like the ST225. One project
that I have on my long-term plate is to tweak the ROMs to handle embedded
SCSI drives (the formatting and partitioning software is *in* the drive
and run by one of its two microprocessors; the PET is completely out of
the loop - it just sends a "N0:diskname,nn" command to the drive and
the drive does all the hard work). It's not exactly the same situation,
but there are similarities - you have to understand the formatter to
know what changes are needed.
> >> >Additionally, whatever (low level) formatting software comes with the
> >> >host might or not might not work with an embedded drive...
> Since whatever replacement drive that I get will most likely come from
> a MS-DOS machine I'll almost certainly have to LL format it. Even more so
> since CPM only handles ~8 Mb partitions. According to the manual I
> SHOULD have both the LL formatting program and something equivelent to
> NEWFS. Again I don't know if I actually have the files. I got a large
> box of SW with the system but loaned it to someone and now he can't find
> it.
Generally speaking, you only have to LL format an embedded SCSI disk if
you are trying to whack and refresh the bad block table because the disk
is aging or you need a different sector size. LL formatting has to be
done *before* partitioning; it's not the _same_ as partitioning.
Think of it this way - in the PC/XT DOS world, you LL format an ST225 drive
with debug the command "G=C800:5" that jumps into the controller's BIOS
You partition with fdisk, and you high-level format with "FORMAT". Three
seperate steps. If your embedded drive works on some other system, you
can probably jump right to "partition" under CP/M, unless for some strange
reason, you can't use 512 byte sectors (almost certainly what your SCSI
drive has on it now, but I _have_ seen other sizes in non-Intel systems)
> What do you think of trying to use some kind of removeable media
> drive such as an IOMEGA ZIP drive or an old Syquest drive?
Should be no different to your host than any other embedded drive. I
don't know about LUN issues, but I wouldn't expect them. I have
both a SCSI ZIP and a 44MB SQ555 (just got a stack of cartridges from
the Micro Center for $3 each, new off the bargain table!) and have
had no compatibility problems on Suns or Amigas or Macs or PeeCees
(would love to try them out on a PDP-8 but I'm still searching for
an OMNIBUS SCSI controller).
> Thanks for your advice. I'll look for a SCSI drive to try our in it. I
> may contact you again if I run into other problems.
No problem. Good luck.
-ethan
P.S. - found an interesting historical document on Segate controllers
and drives at
http://www.mm.mtu.edu/drives/seagate/misc/pc_hints.txt
If you didn't used to have to mess with PeeCee drives 10-15 years ago,
there's some good information in there.
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Received on Tue Jul 23 2002 - 09:30:01 BST