Alright, I have my code running on my real pdp-11/23 now. It works great and I can boot from DU, DD and MU devices. I may add more at some point but for now that's enough. I also have a modified vtserver that can load it via ODT for me.
Thanks again to everyone who helped with pointers and advice! - Peter On Tue, Nov 4, 2025 at 11:12 AM Peter Ekstrom <[email protected]> wrote: > 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 <[email protected]> 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 < >> [email protected]> 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 < >>> [email protected]> 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 < >>> [email protected]> >>> >> 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. >>> >>> [...] >>> >> >>> >>>
