6 Aug
2026
6 Aug
'26
2:33 p.m.
It turned out that the issue with the card reader for the 1401 I/O
diagnostic was caused by a *1410* Card Read instruction without stacking
(M%19) during diagnostic initialization (which is followed by a message
to enter 1401 mod), followed in the actual diagnostic much later by a
1401 SS instruction (which currently the FPGA ignores in 1401 mode),
followed by a read. This was intended to detect whether or not there
was a card reader present and ready for the diagnostic. If I just NOP
the 1410 card read instruction being used to detect the reader, so it
just assumes a reader is present, and only issues 1401 I/O, the 1410
1401 I/O test M014B diagnostic passes. 8^) (The M012A diagnostic does
the same thing, with the same symptoms).
JRJ
On 8/6/2026 2:28 PM, Van Snyder via cctalk wrote:
The FORTRAN II compiler on cards or tape is the same
code. The first
phase works out whether it's loaded from cards or tape. I have the
source for it. I got two operational tapes and reverse engineered them.
Then Gary Mokotoff discovered he hadn't lost his listings when he
retired, and sent me a photocopy. I transcribed it . My code has far
more comments than his. A few of the the tape blocks were too big to
fit through the TAU emulator at CHM so I completely revised its phase
loader, and split a few blocks. The code is
in https://vandyke.mynetgear.com/1401/progs/Fortran/. [1] There's a lot
of clutter at that level so look under Mokotoff for Gary's code, v3m0
and v3m4 for the version reverse engineered from operational tapes, and
v4 for the code revised to fit through the CHM TAU emulator.
Van Snyder
[1] https://vandyke.mynetgear.com/1401/progs/Fortran/.
https://vandyke.mynetgear.com/1401/progs/Fortran/
[2] https://vandyke.mynetgear.com/1401/progs/autocoder/)
https://vandyke.mynetgear.com/1401/progs/autocoder/
I had remembered that you had done that work. Nicely done.
JRJ