If I single-step, it doesn't seem to happen. But I have been playing around with my test program and I added a loop in the beginning that clears 0-377. That loop uses a bne instruction which seems to work fine. When I reach a br or jmp instruction, the program fails. I saw in the opcode test for macro11 in the simtools package, the br instruction is tested with 'br .' so I used that in my program and it failed too.
Now I really need to try this on my hardware 11/23 tonight..... -Peter On Thu, Oct 30, 2025 at 1:03 PM Martin Bishop via cctalk < [email protected]> wrote: > I would verify that what you intended to load has been correctly loaded, > by displaying / dumping 1400 et seq. > If that is good, I would then instruction step to observe where execution > leads. > It may also be necessary to clear the processor's state and maybe issue a > bus init - however, the simulator startup probably obliges. > Martin > > PS FWIW all the vectors and traps (0 to 400 in big handfulls) are > uninitialised (by you), so any of those could take you to exciting places - > eg 5271 > > -----Original Message----- > From: Peter Ekstrom via cctalk <[email protected]> > Sent: 30 October 2025 14:40 > To: General Discussion: On-Topic and Off-Topic Posts < > [email protected]> > Cc: Peter Ekstrom <[email protected]> > Subject: [cctalk] Re: Looking for a bootloader > > 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. > > Below is the listing: > > 1 000000 .asect > 2 014000 .=14000 > 3 014000 012706 002000 start: mov #2000,sp > 4 014004 000240 loop: nop > 5 014006 000776 br loop > 6 .end > > I have a hardware 11/23 but for convenience I have been testing on a SIMH > 11/23 by > loading the binary from the simh prompt and then jumping to the start > address. > I have tested the same code on 11/23+ and 11/70 CPUs and it runs fine. > > I am working in Linux and am using the following Macro11 cross-assembler: > > macro11 - portable MACRO11 assembler for DEC PDP-11 > Version 0.8 (07 Jul 2022) > Copyright 2001 Richard Krehbiel, > modified 2009 by Joerg Hoppe, > modified 2015-2017,2020-2021 by Olaf 'Rhialto' Seibert. > > I then use the obj2bin.pl utility by Don North to convert from object > format to binary load format. > > The following is what happens: > > PDP-11 simulator Open SIMH V4.1-0 Current git commit id: 29d39002 > sim> set cpu 11/23 > sim> load test.bin > sim> g 14000 > > HALT instruction, PC: 005271 (HALT) > sim> > > Am I missing some initialization parts or something? I have looked through > various manuals and the processor handbook for the LSI-11 but if it is in > there, I am missing it. > > Any pointers would be greatly appreciated. > > -Peter > > On Tue, Oct 28, 2025 at 3:38 PM Peter Ekstrom <[email protected]> wrote: > > > Wayne, Warner, Glenn, > > > > Thank you very much for your responses! > > > > Wayne, > > > > I took a look at the PDP11GUI files and it is quite complex. I setup > > the GUI on a PC here and tried it against my PDP-11/23 but wasn't able > > to get it to work. > > Not sure what I did wrong but I am definitely keeping it, and will go > > through that source a bit later. I'm sure I'll learn a lot from it. > > Thank you for the tip! > > > > Warner, > > > > Right now I prefer assembler because I am trying to learn more about it. > > But I glanced at the BSD loader in C and find it quite interesting. I > > am going to go though that too a bit later. Thank you for this tip as > > well! > > > > Glen, > > > > I did look at the sources you mentioned and they were a bit more > > bite-sized. So I have tinkered with it and am actually able to use it > > to boot an 11/23 in SIMH using that code. I have also cobbled together > > a little boot menu and incorporated this loader there. Thank you for > > those pointers! > > > > Thank you all! > > > > -Peter > > > > On Tue, Oct 28, 2025 at 6:38 AM Glen Slick via cctalk < > > [email protected]> wrote: > > > >> (DU) MSCP UDA50(RAxx) disk: > >> > >> https://ak6dn.github.io/PDP-11/M9312/ > >> > >> https://ak6dn.github.io/PDP-11/M9312/23-767A9/23-767A9.mac > >> > >> https://ak6dn.github.io/PDP-11/M9312/23-767A9/23-767A9.lst > >> > >> > >> > >> On Mon, Oct 27, 2025, 4:48 PM Wayne S via cctalk > >> <[email protected]> > >> wrote: > >> > >> > Maybe look at pdp11gui ? > >> > I think it downloads a boot loader so the code may be there. > >> > <https://retrocmp.com/tools/pdp11gui> > >> > PDP11GUI<https://retrocmp.com/tools/pdp11gui> > >> > retrocmp.com<https://retrocmp.com/tools/pdp11gui> > >> > [favicon.ico]<https://retrocmp.com/tools/pdp11gui> > >> > > >> > > >> > > >> > Sent from my iPhone > >> > > >> > On Oct 27, 2025, at 15:58, Peter Ekstrom via cctalk < > >> [email protected]> > >> > wrote: > >> > > >> > I am looking for the assembler listing for a bootloader for > >> > booting > >> from > >> > MSCP disks like RD-disks. > >> > Google has not been very helpful and my assembler knowledge is not > >> enough > >> > for me to write one from scratch. Does anyone have one they can share? > >> > > >> > - Peter > >> > > >> > > >
