18 Apr
2007
18 Apr
'07
5:28 p.m.
Subject: RE: cctech Digest, Vol 44, Issue 47
From: "Barry Watzman" <Watzman at neo.rr.com>
Date: Wed, 18 Apr 2007 13:22:44 -0400
To: <cctech at classiccmp.org>
A friend had one. HT11 was basically RT-11 V2 with V3.* was current.
I have a card cage, lsi-11, memory and serial and parallel IO card set
for an H11. Those were retirees when he went to a 11/23.
HT11 would run on a RX02 though they didn't supply the DX driver (one from
V2.5 worked fine!).
Also the H27 disk system worked fine in any Qbus system when in rx01
emulation mode (using DX driver).
On Tue, 17 Apr 2007, woodelf wrote:
On that subject, what operating systems did the H-11 support? I have
one sitting in my collection, complete with paper-tape reader and 8"
disk drives. Never had the space to set it up until recently.
Steve
The only Heath disk operating system offered by Heath for the H-11 was
HT-11, which was a very slightly modified (dumbed down) version of DEC's
RT-11. The only disk system offered by Heath was the H-27, dual 8" [Memorex
SSSD] drives. Many customers wanted to buy genuine DEC RT-11, which would
run on the H-11/H-27, but it was about $2,500 (and the differences from
HT-11 to RT-11 were very, very few). HT-11 was "cheap", but it would only
run on the H-27, it would not work on a non-Heathkit DEC floppy disk system.
The H-27 had two modes, "Heath" and "DEC", to prevent HT-11 from being
used
on non-Heath H-11's. I don't recall if there was paper tape software for
the H-11 or not (I think
that there was), but even if there was, no one used it very much. The Heath
The paper tape software supplied was IOX or IO executive. It was a package of
routines you could build a closed system around or maybe your own OS.
paper tape reader, the H-10, was a mechanically
unreliable nightmare (mostly
the punch, the reader worked ok), but they are worth a lot of money today,
I've seen them go on E-Bay for over $600.
The punch had a lot of problems and the reader had a cog that would go
out of round.
HT-11/RT-11 was no prize; it was a low level contiguous
file operating
system, less sophisticated even than CP/M, although it may have had some
better utilities (and, for those to whom it mattered, it was of course "more
DEC-like").
Rt-11 is still the same filesystem. However it's a useful realtime OS and
has a very small footprint.
The H-27 was just two standard 8" drives in a case
with a Z-80 based
intelligent controller (WD1771 disk controller chip) that talked to the H-11
using what we would now call a "host adapter" over a proprietary
bi-directional parallel port. The interface and command set wasn't any of
the standards for this type of configuration (e.g. it wasn't SASI or SCSI),
but it used that type of architecture. For a number of years I used an H-27
on an S-100 system with a Tarbell controller by simply disconnecting the
internal intelligent controller and running a 50-pin cable direct to the two
Memorex drives. They were Shugart SA-801 compatible, so it was an easy
configuration to use, the H-27 then being just two drives, a power supply
and a cabinet.
The drives were notorious for broken media hub clamps.
Also the H11 power supply tended to go poof easily.
However for the price it was a huge leap up in performance over the general
market S100 or SS50 machines of the day.
Allison