19 Apr
2007
19 Apr
'07
2:07 p.m.
Ethan Dicks (ethan.dicks at gmail.com) wrote:
I had a vague idea that I didn't want the switch
in the extended
(Heath) position, but I didn't know the specific
consequences.
The [W]H-27 drives were both the best and the most disappointing part of
the H-11 system. BTW, the H-27 was the Heathkit build-it-yourself drive,
and the WH-27 was the ZDS already assembled version. AFAIK they were
otherwise identical.
There's a toggle switch on the front of the drive for "Extended" or
"RX-01" mode. RX-01 mode is completely DEC compatible, and will run RT-11
just fine, but note that "RX-01" really means RX01 - not RX02. Yes, the
[W]H-27 can read/write 512K diskettes, but not in DEC compatible mode.
Bummer!
In extended mode the drive could handle 512K diskettes, and it was capable
of other miracles such as the ability to format a completely blank diskette.
Yes, most people would not be impressed by a drive that can format
diskettes, but real DEC RX01/2 users never knew this joy.
So the bottom line is that if you want to run standard RT-11 on the H-11,
you have to set the switch to RX-01 mode and you have the equivalent of an
RX01 drive. No double density, and no formatting.
Now, HT-11 worked in extended mode and HT-11 also had a program that could
format diskettes. Since HT-11 was basically RT-11, one would think that you
could just install the WH-27 device driver and format program on a RT-11
system and have something that worked in extended mode, but I've never tried
that.
Actually, I don't know what's become of the Heath specific software for
the H-11, such as the WH-27 driver and the format program. Maybe somebody
has an archive somewhere?
Bob