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From: uhclem@trsvax.UUCP
Newsgroups: comp.sys.tandy
Subject: Re: Hard-drives
Message-ID: <193300007@trsvax>
Date: Mon, 23-Mar-87 10:58:00 EST
Article-I.D.: trsvax.193300007
Posted: Mon Mar 23 10:58:00 1987
Date-Received: Sun, 29-Mar-87 18:04:56 EST
References: <9733@topaz.RUTGERS.EDU>
Lines: 61
Nf-ID: #R:topaz.RUTGERS.EDU:9733:trsvax:193300007:000:3278
Nf-From: trsvax.UUCP!uhclem    Mar 23 09:58:00 1987


"Oh yeah?  I can out-wierd anyone laying on this ceiling!"

>I seem to remember that Tandy did something weird with the drive
>interface, don't remember exactly what it was. I'd personally get the
>ProSoft drivers, Tandy has a nasty habit of creating drivers that lack
>flexibility. As far as allocation of space goes you're stuck, the allocation
>scheme for LDOS/TRSDOS wasn't designed with harddisks in mind. You can buy
>a program called "diskdisk" from Misosys, I think thats who sells it, that

The hard disk drivers supplied by Tandy for TRSDOS 6 were completely written
by Logical Systems Inc.  Tandy does not even have a source license for the
LDOS/LS-DOS product line, so don't just assume that Tandy botched the job.
If you purchased "The Source", you have more source than Tandy does.

Yes, there are restrictions in the L.S.I. driver, and most of those are
restrictions of the original Model I directory stragegy for floppies, and
doesn't have a lot to do with the hard disk driver at all. Blame Randy Cook
for not envisioning that the Model I disk format would survive 10 years.
(You can also blame him for only setting aside three bits for the year.)

The L.S.I. hard disk driver "restrictions" are:
o You need to be using the same ports that Tandy picked.  That is, 0xc0 for
  reset, enable, interrupt and WP status, 0xc8 to 0xcf map directly to
  the 8x300/WD1010 port decoding.  See those manuals for details.

o You can only use 8 heads and 404 cylinders on a disk.  This is due to
  the GAT size limitation.
o The precomp is hardwired to be the half-way point on the disk.  All disk
  manufacturers I know say it is ok for precomp to come on early, and most
  newer bubbles ignore the signal from the controller and their on-board
  microprocessor turns the precomp on at the right cylinder.
  If you need some other value for your controller, patch it.  There should
  be plenty of room.  If you need an address, send me some mail.
o The step rate can be set to any value supported by the 8X300/1010 controller.
  All Tandy drives use the 50usec buffered seek, but the other speeds do
  work.
o The granule size varies with the disk size.  Yes, your 1 character files
  can take up 8K, but when you only have 202 8 bit words to describe an
  entire cylinder (worst case), you are forced to the high granularity.
  You should consider using DiskDisk or building library-style files for
  those smaller executables.

When L.S.I. spun off it's utility business to Misosys (owned by Roy Soltoff,
who worked on LDOS and the first TRDSOS 6.0.0 release), diskdisk did
become available only from Misosys.  Diskdisk is a very nice utility
and lets you do neat things like exact images of floppies on your
hard disk for mirror image backups, as well as implement a clumsy form
of subdirectory support.


<This information is provided by an individual and is not nor should be
 construed  as  being  provided  by  Radio  Shack or Tandy Corp.  Radio
 Shack/Tandy Corp has no obligation to support the information provided
 in  any way.   Its  just that  I happen to  know what  was  going  on,
 something  about  testing it,  writing the documentation,  getting the
 bugs fixed, you know.>
						
						"Thank you, Uh Clem."
						Frank Durda IV
						@ <trsvax!uhclem>