December 22, 2025 Categories Reading time: 3 minutes

A few weeks ago a copy of Unix V4 which was thought to be lost was discovered on a storage tape at the University of Utah. It was then sent to the Home Computer Museum in California, and well, they managed to read it out and put its contents on the Internet Archive.

I haven’t seen any news articles about this yet, but fellow Mastodonian Flexion gave it a try and posted about it, which is how I came across this. So I had to try it, too.

Thankfully someone put up a tutorial with the necessary files here. All that’s needed is a pdp11 emulator. I’m using the one from the Open SIMH project which I could easily download on Arch Linux from the repos, it’s just called simh.

And from there it was just a matter of following the tutorial. I had to get four files:

• unix_v4.tap
• disk.rs
• install.ini
• boot.ini

I put them all in the same folder and started the pdp11 emulator with the ini script:

$ simh-pdp11 install.ini

Then I followed the tutorial by typing out the following commands:

=mcopy
'p' for rp; 'k' for rk
k
disk offset
0
tape offset
75
count
4000
=uboot
k
unix
mem = 64530

login: root
# sync
# sync
# sync
# ^E        ; end emulation

After Ctrl+E the emulator can be quit with Ctrl+C and then restarted with the boot script:

$ simh-pdp11 boot.ini

After typing k and unix I got the login prompt and could log in as root:

k
unix
mem = 64530

login: root
#

And there we go, Unix V4 from 1974!

So what can we do with that?

Honestly, I have no idea. Not too much probably, but it’s really cool to explore and just to see it running. This system is almost a decade older than I am, and it feels kind of alien and still familiar at the same time. It was made at a time when computers were the size of refrigerators and often didn’t even have monitors yet but instead printed their output on a piece of paper. And yet It’s the ancestor to all modern day Unix systems (including MacOS) and also at least the spiritual ancestor to Linux, and that’s exacty what it feels like using it. Like an early version of these systems. Relatively primitive and missing a lot of features that make using the modern systems easy, but definitely familiar.

It’s fascinating to see how much it has changed in the last 50 years, but also how much has stayed the same. It’s a bit like driving in a car from the 60s or 70s. They are incredibly barebones by today’s standards, but still unmistakably just an earlier version of what we have today and if you know how to drive a modern car, you will also be able to drive one from 1974, just like you are able to navigate around a Unix system from 1974 if you’re familiar with it’s modern descendants.

Want to get in touch?

• [Send me an E-Mail](mailto:andreas@82mhz.netDELETEME?subject=Post %22Running Unix V4 from 1974%22 “email me”)
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