This repository contains the code originally written by Paul Nankervis to emulate a number of the PDP 11 series microcomputers by Digital Equipment Corporation (DEC).
The code in this repository originally lived (and continues to live until further notice) on Paul's site located at this address: https://skn.noip.me/pdp11/pdp11.html
Permission was given, by Paul to upload his source code to GitHub. This is the result of that work.
There are two demo's currently live. The first version, complete with all of the original disk images, can be found on Paul's original site: https://skn.noip.me/pdp11/pdp11.html
If you don't think you need access to the disk images, you can access the emulator directly from GitHub Pages, here: https://jameshagerman.github.io/nankervis-pdp11-js/pdp11.html
Most of the following notes were extracted from Paul's original PDP 11 page. Some formatting issues may exist, and some re-organization may have taken place for clarity. Some links may be broken, but should be working on the original site.
In case things are unclear, be sure to check things on Paul's original site as things may have been lost in translation.
This emulator came about because years ago I was a programmer for RSTS/E on a PDP 11/45 and had admired the console idle loop light pattern - but I couldn't quite remember how it looked. Given the unavailability of real systems it became time to write an emulator!
I was going to start with a PDP 11/45 emulator but the extra memory of a PDP 11/70 became far too attractive (a whole 4MB!). It took some time before I finally produced a PDP 11/45 version.
I have met my core objective - I can now see the RSTS/E console light pattern that I was looking for, and found that newer versions (eg v9.6) have a different light pattern. Also I have now seen some of the light patterns for other OSes. RSX and BSD 2.11 have their own different patterns and Unix V5 and Ultrix operate with absolute minimum light movement (I'm assuming they operates mostly in WAIT mode).
Getting all of the operating systems used here presents its own set of challenges - one of which is finding the software in the first place. But one of the most interesting was RSTS/E V06C which has its own story.
Note: The boot code in this emulator is a custom PDP 11 program running with it's own set of light patterns. It is initially loaded at address 140000 and the LIGHTS command operates by mapping a WAIT instruction to different addresses within Supervisor mode. The source for this program can be found in the RT11 operating environment as BOOT.MAC You can use this code to boot one of the guest OSes or use the LIGHTS command and DIAG command to experiment with idle light patterns and load test the CPU.
If you wish to toggle in a simple light chaser to the front panel then here are some switch commands which can be used:
Address Data Code Switch commands
HALT, 001000, LOAD ADDRESS
001000 012700 mov #1,r0 012700, DEPOSIT
001002 000001 000001, DEPOSIT
001004 006100 rol r0 006100, DEPOSIT
001006 000005 reset 000005, DEPOSIT
001010 000775 br .-4 000775, DEPOSIT
001000, LOAD ADDRESS, ENABLE, START
To restart the initial boot code (if it has not been overwritten) use the switch commands:
HALT, 140000, LOAD ADDRESS, ENABLE, START
If you plan to run the emulator repeatedly or for a project, consider downloading the emulator to your own machine or server. This will significantly speed any of the emulator disk accesses and response times. All files and emulator OS disks can be found in the top level folder of http://skn.noip.me/pdp11/ or in the single zip file http://skn.noip.me/pdp11/pdp11.zip
This emulator matches approximately the following SIMH configuration:
set cpu 11/70 1912K nofpp !1912K is not actually SIMH legal - use 2M instead
set clk 50hz
attach rk0 rk0.dsk !RK05 image of Unix V5
attach rk1 rk1.dsk !RK05 image of RT11 v4.0
attach rk2 rk2.dsk !RK05 image of RSTS V06C-03
attach rk3 rk3.dsk !RK05 image of XXDP
attach rk4 rk4.dsk !RK05 image of RT-11 3B
attach rk5 rk5.dsk !RK05 image of RT-11 V5.4F
set rl0 RL02
attach rl0 rl0.dsk !RL02 image of BSD 2.9
set rl1 RL02
attach rl1 rl1.dsk !RL02 image of RSX 11M v3.2
set rl2 RL01
attach rl2 rl2.dsk !RL01 image of RSTS/E v7.0
set rl3 RL02
attach rl3 rl3.dsk !RL02 image of XXDP+
set rp0 RP06
attach rp0 rp0.dsk !RP06 image of ULTRIX-11 V3.1
set rp1 RP06
attach rp1 rp1.dsk !RP06 image of BSD 2.11
set rp2 RP04
attach rp2 rp2.dsk !RP04 image of RSTS/E v9.6
set rp3 RP04
attach rp3 rp3.dsk !RP04 image of RSX 11M v4.6
attach tm0 tm0.tap !Backup of RSTS 4B-17
attach tm1 tm1.tap !Distribution for RSTS V06C-03
attach tm2 tm2.tap !Distribution for RSTS V7.0
This emulator then loads in the BOOT.MAC code to location 140000 and begins execution there. There are many PDP emulators out there and I have never seen what I consider to be a complete list. Some of the really interesting ones can be found by googling terms such as "vhdl pdp 11". However the gold standard seems to be SIMH at Trailing Edge. A different approach to Javascript PDP 11 emulation can be found at www.pcjs.org.
I believe that the first PDP 11 emulator would be SIM-11 written in FORTRAN before the first PDP 11/20 hardware was even built - see How the PDP-11 Was Born. There is more PDP 11 history at www.hampage.hu.
Of course if you want your own PDP 11/70 front panel you might consider one of these.
Happy emulating!
Paul Nankervis
Note: Due to the size of some of these images, they are not included in this GitHub repository themselves. Instead, they can be found on the Releases page of this repo, or on Paul's original site. If using the Releases version, extract the archive and place the *.dsk and *.tap files in the os-images/ directory inside this repository.
Disk OS Comment
RK0 Unix V5 Boot using: unix then login as root
RK1 RT11 v4.0 The lightest/fastest OS here
RK2 RSTS V06C-03 Boot and login as 1,2 with password SYSTEM or as 11,70 using PDP
RK3 XXDP Diagnostic OS and utilities
RK4 RT-11 3B Distribution for RT-11 Version 3B
RK5 RT-11 V5.4F Distribution for RT-11 Version 5.4F
TM0 RSTS 4B-17 Boot ROLLIN from TM0 and restore DK0 with "DK:<MT:VIXEN/REW". Reboot from DK0 with "/BO:DK" and login as 1,2 with password SYSTEMor 11,70 using PDP Commands are case sensitive.
RL0 BSD 2.9 Boot using: rl(0,0)rlunix CTRL/D to get to multiuser
RL1 RSX 11M v3.2 Login as 1,2 with password SYSTEM
RL2 RSTS/E v7.0 Option: <LF> Suboption: <LF> ... Login as 1,2 using SYSTEM or 11,70 using PDP
RL3 XXDP Larger version of diagnostics - including PDP 11/70 utilities
RP0 ULTRIX-11 V3.1 CTRL/D to enter multiuser mode. Login as root with no password
RP1 BSD 2.11 Will autoboot and enter multiuser mode. Login as root with no password
RP2 RSTS/E v9.6 Answer boot questions and login as 1,2 (password SYSTEM) or 11,70 (no password)
RP3 RSX 11M v4.6 Starts logged in as 1,2 (password SYSTEM) - user accounts 200,1 (no password) or 11,70 (password PDP)
Note: Disks are shown in approximately order size. The RK05 disks at the top are small and not too bad to use across a network. The RP06 disks at the bottom can be rather slow.
Note: This text was originally hidden at the very bottom of Paul's Index. I didn't see it until moving it into this repo, so I moved it here for better visability.
Plenty! Especially in the places where I haven't managed to figure out what a real PDP 11/70 should do. :-( Core PDP 11/70 stuff is well documented but some lesser used system functions require reverse engineering to understand.
If you have something you want me to look at let me know and I'll prioritise. However always happy to accept fixes!
Note: Now that this code exists in GitHub, it may be prudent to both follow Paul's original advice and reach out to him, as well as open a GitHub issue. Keep in mind, the later may not be productive...
Originally, these example boot logs were in the pdp11.html file. They've been moved to another file in this repo named ExampleBoots.md, found here.
The examples are seriously work looking through!