Sam11 - a PDP-11 emulator for microcontrollers

This appeared on Hackaday a couple of years ago, and I recently discovered it when searching for something else.


My first introduction to Unix was v6 running on a PDP 11/40 (c1980, so late to the game!) I’m fairly sure that system was upgraded to run v7 at some point, so a little confused by the “not enough” quote above…

I do recall the magnetic core was replaced with DRAM which ran at double the speed as no write-after-read was needed and a new hard drive added (20MB?) to replace the smaller RK05. (It had an RK05f to boot from an a removable one for various projects)

I remember the RAM upgrade process - the chap in charge of it gambled that by not paying for a quarters maintenance on the core he could then afford the DRAM upgrade - with vastly reduced on-going maintenance fees too.


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Not to be confused with the MIMIC PDP-10 assembly simulators of PDP-8s and PDP-11s that the SimH simulator is based on (yes, simh is a port of code from the 70s!)


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Interesting! Didn’t know that about SimH.

I cut my teeth on an 11/34 running RSTS/E

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I thnk there might be a need for good introduction of how to setup simh to run
pdp 11 operating systems since that older knowlage is not so easy to find anymore.
I am thinking more virtual hardware setup, and starting a OS to get the user promt
after mounting drives and configuring terminals.
“How do I set SIMH to give me a real serial port?” for example.

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Yes, SIMH has very poor docs. I never liked SIMH.
But as for most emulators (especially without GUI), someone has to know the hardware and the software. And then check how it’s implemented in SIMH. Even for simple stuff like attaching devices.

Some time ago, I found some FAQs and personal manuals for SIMH especially for PDP10 and/or 11.

I also wonder why there are so few tools. Someone still needs PUTR and DOS.

For some machines, SIMH is the only or best emulator. But for my PDP8 stuff, I rarely use it.

What do you use for your PDP-8 emulation/simulation? I have also had troubles with SIMH, although honestly I haven’t put a huge amount of effort into it.
I do have a 4K PDP-8 emulation running on an Arduino Mega (GitHub - KedalionDaimon/DEC-PDP-8-on-Arduino: DEC PDP-8 emulator running FOCAL 69 in 4K for Arduino DUE and Arduino MEGA 2560) which runs 4K FOCAL. It’s really cool, but I would like something with a bit more muscle (brain?) power.

As said on my Festo threads, I use different emulators and tools.

This online emulator is very good, showing MA and MB, and you can change any bits. Also a good export disassembly list including Sixbit characters.

Best (GUI) emulator is a Mac one (MACOS9 and MACOS10).

My favourite one is a command like one called pdp8emu also running under linux. Easy to use and knows almost all opcodes. And very good trace run. File needs to be converted via tape2bin (without leader,trailer).

GitHub - mengstr/pdp8emu: PDP8 emulator running in console. Based on Douglas W. Jones code from 1995

Another great 2-pass tools are d8tape and scripts like bin2pal by Vincent Slyngstad.

f.w.i.w.: I also created a PDP11/70 emulator for a microcontroller series (ESP32).
Mine can also (altough only on linux yet) do snapshotting and can run UNIX7 multi-user.