Hi, All,
After years of looking, thanks to a tip from this list, I finally have
a VT-78 to play with. I got a complete WPS-78 system except for the
cart - CPU, RX78 floppy enclosure, and DEC-badged Diablo Hytype? II
daisywheel printer and all the cables. So far, everything checks out.
The CPU came with an MR-78 ROM pack on it. For those that might not
know, it's an optional bolt-on firmware box that attaches to a DB25
plug and simulates a high-speed papertape reader. From reviewing the
MR-78 printset (at the end of some of the electronic copies of the
VT-78 printset), it appears that DEC sold it with several sets of
firmware - there's at least a WPS78 load and a diagnostic firmware
load, and possibly one or two more.
Are there any ROM dumps of the MR-78 anywhere? In all my years of
collecting PDP-8 parts and software and docs, I've never seen any, but
I might as well ask. The circuit is utterly trivial to reproduce,
and, of course, the size of modern ROMs would make it a no-brainer to
make an uber-MR-78 with all known versions of the firmware on it, or
with user-definable content as well (the code is stored as 8-bit bytes
simulating a papertape stream (either BIN or RIM (have to check the
"panel ROM code" to see which one) with some functionality removed (no
RUBOUT, no pauses, and such)). Obviously I can dump the one I have,
but it would be interesting to review the contents of the others.
Thanks for any pointers on the MR-78 and its contents.
-ethan
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