[cctalk] Re: Looking for a bootloader

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 &lt;epekstrom(a)gmail.com&gt; 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&gt; 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&gt; 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&gt; >> >> 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. >> >>> [...] >> >> >> >>