Is the SimH emulator available for macOS? I can't find it on their website: http://simh.trailing-edge.com/

What I am specifically interested in is to run UNIX V7 on a PDP-11 emulator.

4 Answers 4


It’s available in Homebrew for macOS; install that, then

brew install simh

to install SimH.


What homebrew will install for you on MacOS as of today (Aug. 30 2017) is simh V3.9, which does look to be the latest non-beta release at present.

A beta release of simh V4.0 is available that is also supported on current and recent versions of MacOS. You can find it at https://github.com/simh/simh if you're interested. V4.0 introduces support for emulating quite a few new processors and variants of already supported processors, as well as many enhancements to simh itself.

  • 2
    Welcome to Retrocomputing Stack Exchange. Thanks for the answer. It would be useful if you could edit it so that it contains enough information to answer the specific question "Is the SimH emulator available on macOS?" - at present it doesn't give this information.
    – wizzwizz4
    Aug 31, 2017 at 9:32

You can also install simh from MacPorts; to install it do:

port install simh

As the time of this writing, MacPorts is installing simh V3.8-1.

I am also adding how to run Unix System 7, as I found a couple of inconsistencies in the original instructions:

Now for putting it to work with Unix system7, download the PDP 11 Unix 7 tape image from http://simh.trailing-edge.com/kits/uv7swre.zip

Then unzip either double-clicking on it, or with ´unzip` from MacPorts:

unzip uv7swre.zip

If you have now new subdirectories, go inside them until finding the unix_v7_rl.dsk file. Put it in a directory of your convenience.

To boot then it, use the simh-pdp11 as it is que equipment you need to emulate to run your image:

$ simh-pdp11
PDP-11 simulator V3.8-1
sim> set cpu 11/45
Disabling XQ
sim> set tto 7b   
sim> attach rl unix_v7_rl.dsk    
sim> boot rl
New Boot, known devices are hp ht rk rl rp tm vt 
: rl(0,0)rl2unix
mem = 177856

If it is the first time booting the image, create the missing directories of Dennis Ritchie´s user home, and /tmp:

# mkdir /usr/dmr
# chown dmr /usr/dmr
# chgrp 3 /usr/dmr
# mkdir /tmp
# chmod 777 /tmp

Then press ^D to proceed:

# Restricted rights: Use, duplication, or disclosure
is subject to restrictions stated in your contract with
Western Electric Company, Inc.
Thu Sep 22 05:48:15 EDT 1988

login: dmr

The dmr user has no password by default.

If you need to login as root, by default, in this tape image, the root account has as password, root.

For leaving the emulation:

$ sync
$ sync
$ ^E
Simulation stopped, PC: 002306 (MOV (SP)+,177776)
sim> quit
  • 1
    I ran through the instructions and I can confirm they work beautifully. Bit of a shocker to see how little Unix v7 had. Not even vi.
    – JeremyP
    Feb 12, 2018 at 16:53
  • @JeremyP While this tape image is very interesting historically, the PDP 11 tape of the sys V one is far more, having C sources. Will probably make a post detailing the installation in the next couple of days. I still have an improvement to make here today or tomorrow if I find my old backups, stay tuned. Feb 12, 2018 at 16:55

However if you need network support install Tunnelblick's kernel extension. The config looks like this:

! kextload -v /Applications/Tunnelblick.app/Contents/Resources/tap-notarized.kex
SET XQB ENABLED                                                                 
SET XQB MAC=08-00-2B-AA-BB-CE                                                   
SET XQB TYPE=DELQA-T                                                            
ATTACH XQB0 tap:tap0                                                            
! ifconfig tap0 netmask up                         

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .