20 Jul
2014
20 Jul
'14
7:46 a.m.
Eric Smith wrote:
On Sat, Jul 19,
2014 at 9:52 PM, Jerome H. Fine <jhfinedp3k at compsys.to> wrote:
Although the VT14 was not intended to run PDP-8
software, was or would it have been possible?
I don't think so, without rendering it effectively no longer a VT14.
The VT14 was specifically a terminal to program a PDP-14 using ladder
logic, had ROM firmware that only did that, and had only 1K of RAM,
not contiguously mapped. It had an alphanumeric display, but not an
alphanumeric keyboard, though it normally is used with a teletype for
printing ladder diagrams and punching and reading paper tape. You
could presumably reprogram or replace the MR8-F ROM, and add more RAM,
to use it as a general purpose computer.
The built-in video terminal wasn't really a VT8-E, though perhaps the
electronics may be similar. The VT14 uses the M7441 and M7443
modules, while the VT8-E uses the M8335, M8336, and M8337. The
housing is definitely not the VT8-E/VT05 housing.
In other words, as supplied, the VT14 is a lot further from being
usable as a general-purpose computer than the VT103.
from 18 bits to 22 bits (so that the maximum memory
which the Qbus PDP-11
CPU could use was supported rather than only the 256 KB of
memory which
was supported by the DEC configuration) did not prevent any prior use of the
VT103 since using only a 256 KB memory board was backward compatible.
IN ADDITION note that since your last sentence suggests that the VT103
is not "usable as a general-purpose computer" even in its original
configuration
as supplied by DEC, it seems helpful to correct that (possible?)
misunderstanding!
Although the exercise might have been painful (in the extreme), using a
TU-58
drive to run RT-11 was possible - the user just had to be a bit patient and
remember that just booting RT-11 could take many minutes. At that point,
(with the TU-58) the VT103 was already a general-purpose computer, but
from a user's point of view so painfully slow that
it was still not
really very
useful. Adding the dual board RX02 Qbus controller (which even the power
supply of the VT103 could easily support - although the user would need to
spend up to a minute to manually type in the boot code when the CPU card
was just a dual board, but that was still much less time than to boot with a
TU-58) along the external RX02 dual drive transformed the VT103 into a
very usable (if slow) general-purpose computer, although at higher cost than
a TU-58 drive.
BUT, adding a third party hard disk drive controller (I did that for
both myself
and a number of VT103s for a commercial outfit) which included a boot ROM
for an MSCP device (which was extremely helpful when only dual board DEC
CPUs were being used which had no boot ROM - DEC did supply them
with quad board CPUs) and also placing a 10 MB ST512 drive just below the
tube of the VT103 which was compatible with that third party hard disk
controller instantly made the VT103 into a very usable general-purpose
computer. Later, substituting instead a CQD 220M/T host adapter and a
3.5" SCSI hard drive provided the VT103 with more than sufficient disk
capacity.
SO if the VT14 could not be easily adapter to run PDP-8 software, then
I agree that is was not in the same sort of ball park as was the VT103
which could already run PDP-11 software (even if painfully) in the
original DEC configuration. I did appreciate the clarification.
Jerome Fine