4 Nov
2025
4 Nov
'25
8:12 a.m.
All,
Thank you for all your help and suggestions! The test program and the
bigger program I am working on both work reliably on an 11/23 CPU now.
When I tried the bigger program on my hardware 11/23 I had problems. It
randomly jumped to odd places and crashed. Because it is big, a little
over 1KB, I use a modified vtserver to help me load it. Using ODT and a
halted CPU to single-step, I found out that some of the words loaded by
vtserver weren't the right ones. After looking at it some more, it seems
vtserver has problems with the higher-value instruction words and ends up
loading something completely different. So I'll have to look closer at
vtserver and see why that is. I tried lowering the baud rate of the console
but
that made no difference. So it appears to be a problem with vtserver at
this point. I manually went through the affected locations and corrected
them.
After that the program ran great and I was able to boot up RSX11M from an
RD53.
- Peter
On Tue, Nov 4, 2025 at 11:03 AM Peter Ekstrom <epekstrom(a)gmail.com> wrote:
Hi Jos,
Thank you for pointing this out. I feel I should have known that. :) I
must have glossed over that when I was looking through the manuals.
- Peter
On Sat, Nov 1, 2025 at 2:28 PM Jos Fries via cctalk <cctalk(a)classiccmp.org>
wrote:
> Peter,
>
> Single-stepping a PDP-11/23 is done by putting the HALT switch in the
> down (Halt) position and then issuing the Proceed or Go command. See the
> KDF11-A User’s Guide par. 3.4.7.
>
> Jos
>
> > Op 1 nov 2025 om 13:58 heeft Peter Ekstrom via cctalk <
> cctalk(a)classiccmp.org> het volgende geschreven:
> >
> > Hi Jay,
> >
> > Thank you for this information! I didn't think of trying that. Paul's
> > suggestion to set PSW to 340 and a reset works as well.
> > But it is good to have more options. :) Now to figure out why it won't
> run
> > on my hardware 11/23. Is there a stand-alone
> > debugger for bare metal stuff? I'd like to be able to single-step but
> ODT
> > doesn't have that ability. Got spoiled by SIMH.
> >
> > - Peter
> >
> >> On Sat, Nov 1, 2025 at 7:23 AM Jay Logue via cctalk <
> cctalk(a)classiccmp.org>
> >> wrote:
> >>
> >> Classic stray LTC interrupt. You can disable LTC interrupts in simh by
> >> setting the NOBEVENT option (11/23 and 11/03 only). This simulates
> >> disabling the LTC via the front panel switch or a jumper on the CPU
> >> board. E.g.:
> >>
> >> $ pdp11
> >> PDP-11 simulator V4.0-0 Current git commit id: 5cfa8662
> >> sim> SET CPU 11/23
> >> sim> SET CPU 32K
> >> sim> SET NOBEVENT
> >> sim> RESET
> >> sim> load loop.bin
> >> sim> g 14000
> >> ^E
> >>
> >> Simulation stopped, PC: 014006 (BR 14004)
> >>
> >> Note that a RESET is need after NOBEVENT is set in order for it to take
> >> effect. This is because the NOBEVENT option effectively changes the
> >> default value of the Interrupt Enable bit in the LTC control register
> >> upon a system reset.
> >>
> >> --Jay
> >>
> >>> On 10/30/25 07:39, Peter Ekstrom via cctalk wrote:
> >>> Anyone here familiar with programming the 11/23 (KDF11-A) in
> assembler,
> >>> bare metal?
> >>> I have been trying to get a very simple test program to run on it but
> it
> >>> keeps halting on
> >>> an address outside of the program. Seems to always be the same address
> >>> which is why
> >>> I am thinking I must be missing something. The program runs fine on an
> >>> 11/23+ or 11/70.
> >>> [...]
> >>
>
>