f637c210
From: uhclemLOSE.sep08@nemesis.lonestar.org
Kelly Leavitt wrote:
: What is the "correct" version of TRS-DOS for the Model 12. I know
: there were many versions.
:
: Anyone (Mr. Durda?) know which ones run correctly on a Model 12?
It depends on a couple of factors, notably if you have hard disk drives
and if you have enough RAM in the right places.
Because a Model 12 came with thinline drives, at minimum it can run
TRSDOS 2.0B. "B" is the version of 2.0A patched to deal with the
spin-up time of the thin-line drives. "A" assumes older drives with
constantly spinning motors.
TRSDOS 2.x does not support hard disk drives, but was initially
required to build a TRSDOS-II 4.0 hard disk format and install the OS.
(TRSDOS-II 4.2 and later releases system floppies could build their
own hard disk systems.)
In the TRSDOS-II family, you need 64+16K of RAM. The extra RAM could
either be on the hard disk interface board, in the extra row of sockets
on the Model 12/16B/6000 motherboard, or the 68000 memory card.
(Or you could have a rare memory card that could support two rows
of 64K of RAM which was meant for use in the Model II/16.)
The additional 16K is used for OS overlays and buffers.
If you are just running floppies and have sufficient RAM, any of the
TRSDOS-II 4.2.x releases will do, but the 4.2.7, 4.2.8 or 4.2.9 would
have the most fixes. It assumes you have thinline drives, but you
can optionally change settings to get a bit more performance out of
the older style drives.
At one time there was a plan to try to slim TRSDOS-II back down to fit
in 64K or at least function on systems with only 64K, but I do not
recall if that ever went anywhere. Unfortunately, that system had a
lot of bloat that made it big and slow. Part of that came from the
decision that TRSDOS-II maintain the illusion of 256 byte records on a
system where the actual disk block sizes were now all 512 bytes.
This made the OS internals very convoluted.
The idea of *not* having or managing record size concepts within the OS
(like UNIX, which optionally provides that in the libraries or the
individual progrems themselves and not in the OS) was still considered
a radical and over-simplistic approach (particularly by the IBM mainframe
programmers of the data processing world of that day), and so all the
TRSDOS operating systems provided traditional fixed record format
concepts as persistent attributes of the files as well as having that
concept permanently wired into the OS I/O routines.
TRSDOS-II 4.3 (notably TRSDOS-II 4.3.11i) was meant for systems with
an ARCNET card, and it may not work if that card is not present.
That was sort of a side-branch from the earliest 4.2 releases.
TRSDOS-II 4.4 (never released via retail) is based on the last 4.2
releases, and eliminates the need for a specific release for the different
types of MFM hard disk controllers that were in machines at this time.
It is somewhat faster than any of the 4.2s with new features.
A Model 12 likely shipped originally with a TRSDOS 2.0B and either a
TRSDOS-II 4.1/TRSDOS-16 system diskette, or later a TRSDOS-II 4.2.x
diskette. Depending on the date of ship, you had a choice of two or
three operating systems in the box with the computer. Or you could
run some third-party OS (LS-DOS, CP/M, etc).
Model 12s should have shipped in a configuration to meet the 64K+16K
requirement of TRSDOS-II. I have noted some systems that have been
for sale in recent years no longer have the hard disk interface card,
and so now only have 64K of RAM and can only run TRSDOS 2.0B.
Frank Durda IV - send mail to this address and remove the "LOSE":
http://nemesis.lonestar.org
"The Knights who say "LETNi" demand... A SEGMENT REGISTER!!!"
"A what?" "LETNi! LETNi! LETNi!" - 1983
Copyright 2008, ask before reprinting.
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