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Unix v4 Tape Found

510 points| greatquux | 3 months ago |discuss.systems

https://oldbytes.space/@bitsavers/115505135441862982

https://www.theregister.com/2025/11/07/unix_fourth_edition_t...

https://www.tuhs.org/pipermail/tuhs/2025-November/032758.htm...

100 comments

order

lproven|3 months ago

Anyway, since nobody much seems to realise this is quite a big deal, I will share the explainer I wrote yesterday:

https://www.theregister.com/2025/11/07/unix_fourth_edition_t...

Unix V4 is otherwise lost. It was the first version in C.

avar|3 months ago

    > This is rare enough that I'm pushing the recovery
    > of it up near the top of my project queue.
The reader is left to wonder what the software librarian at the Computer History Museum could have possibly found recently that warrants a placement ahead of Unix v4 in their project queue. A copy of Atlantian Unix from the ancient Library of Alexandria?

mongol|3 months ago

Interesting article. I agree it is kind of a big deal. Certainly worth the effort to try to restore

reactordev|3 months ago

Please let there be an ultimate force in the universe that spared this tape from tape degradation and/or magnetization that it can be read and extracted into a raw dump fs that we can preserve for all time. (fingers crossed)

Tapes from back then haven’t held up over the years. It all depends on the environment it was stored in.

dmix|3 months ago

I remember reading we're nearing a timeframe where VHS and cassette tapes made in the <=1980s will start degrading pretty seriously. So if you own lots of VHS or camcorder tapes you have a relatively short window to save old family videos... or just deal with fuzzy images and bad audio.

tgtweak|3 months ago

There is one parity bit per 8 data bits, which is decently resilient - plus the recovery is pretty simple on the occasional bit flip. Combine that with the fact you can reference other sources to make up for missing/corrupted files - I think the chance that this is recoverable is pretty high provided the machine reading it is high quality. Checksumming on the source was unfortunately not commonplace until Unix 7, so it's unlikely there was any software-level integrity checks here. The tape looks like it was stored in a sealed container which is a very good sign. Those older tapes are actually more resilient than the later generation of tapes, and don't usually degrade the same way even with exposure to humidity.

whizzter|3 months ago

Someone in the Mastodon thread mentioned the Andrew Tannenbaum "Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway."

So I wondered about a modern day equivalent, looked up 1tb micro-sd cards (sold locally for Nintendo Switch) and calculated that there'd be roughly space for 400 exabytes of data in a shipping container filled to the brim with SD-cards.

(SDcard being 1tb for 1.092 x 1,499 x 0,102 CM's and a shipping container being 1203 x 235 x 239 CM's inside so holding 400 million SD cards)

avar|3 months ago

Actually a shipping container full of micro-SD cards hurtling down the highway has lower overall bandwidth than a 56k modem.

That's because whoever's attempting to load an ideal 400 million micro-SD cards into one will take approximately forever carefully trying to line up even one row of them on the floor of a shipping container, before having the whole thing fall over like dominoes.

And even if they manage that, the whole thing will tumble over once they need to deal with the first row of the container's side corrugation. Nobody at the department of Spherical Cows in Vacuums thought to account for those dimensions[1] not lining up with the size of micro-SD cards.

If they do manage some approximation of this it'll take forever just to drive this down the road, let alone get the necessary permits to take the thing on the highway.

Turns out not a lot of semi truck trailers or roads are prepared to deal with a 40 ft container weighing around 100 metric tons (the weight of one packed to the brim with sand, a close approximation).

The good news is that such transportation gets more fuel efficient the longer the trip is.

The bad news is that the container will arrive mostly empty, as it's discovered that shipping container door panel gaps and road vibrations conspire to spread a steady stream of micro-SD cards behind you the entire way there.

Commuters in snowy areas held up behind the slowly moving "OVERSIZED LOAD!" with a mandatory police escort wonder if it's a trial for a new type of road salt that makes a pleasant crunchy sound as you drive over it.

Finally, an attempt to recover the remaining data fails. The sharding strategy chosen didn't account for failure due to road salt ingression into the container, cards at the bottom of the container being crushed to dust by the weight of those above, or that the leased container hadn't been thoroughly cleaned since last transporting, wait, what is that smell?

1. https://www.discovercontainers.com/wp-content/uploads/contai...

compsciphd|3 months ago

I used to be a digitial hoarder (now less so, but I still have what I hoarded, built over a 15 year period). When I moved overseas, I shipped my 120HDs (~600TB) in a container (120 HDs don't take up "that" much space (they all arrived in one piece, though 5 have died, though only 3 non recoverable, after the first one died, I made sure to image each one first and then writing it back (bitrot was a problem)).

anyways, in took 2-3 months for it to arrive (and most of that time it was waiting in either port), but by my calculation, I have needed to transfer it at a consistent 80MB/s or so (close to gigabit) to be able to net the equivalent transfer rate.

accrual|3 months ago

> It is a '70s 1200ft 3M tape, likely 9 track, which has a pretty good chance of being recoverable.

Not old enough to have this kind of knowledge or confidence. I wonder if instead one day I'll be helping some future generation read old floppies, CDs, and IDE/ATA disks *slaps top of AT tower*.

retrac|3 months ago

You might be able to use that old floppy drive. But you won't be able to use that old Pentium machine the drive is in.

Because you will need several hundred gigabytes of RAM and a very fast IO bus.

The gold standard today for archiving magnetic media is to make a flux image.

The media is treated as if it were an analog recording and sampled at such a high rate that the smallest details are captured. Interpretation is done later, in software. The only antique electronics involved are often the tape or drive head, directly connected to a high speed digitizer.

And indeed that appears to be the plan Al Kossow has for the tape: https://www.tuhs.org/pipermail/tuhs/2025-November/032765.htm...

As for CDs, I don't see the rush; the ones that were properly made will likely outlast human civilization.

codezero|3 months ago

Just anecdata, but I had this concern when I worked in academia and we backed up all our data to writable DVDs. I was there 10 years after the start of the project and I periodically checked the old DVDs to make sure they weren't corrupted.

After 10 years, which was longer than the assumed shelf life of writable/rewritable DVDs at the time, I never found a single corrupt file on the disks. They were stored in ideal conditions though, in a case, in a closed climate controlled shelf, and rarely if ever removed or used.

Also, just because I think it's funny, the archive was over 4000 DVDs. (We had a redundant copies of the data compressed and uncompressed, I think it was like 3000 uncompressed 1k compressed) there was also an offsite redundant copy we put on portable IDE (and eventually SATA) drives.

satiated_grue|3 months ago

Take a look at floppy disk controllers like the AppleSauce, Greaseweazle, and Kryoflux for preserving floppies by recording at the flux-transition level.

don-code|3 months ago

This seems to be how a lot of modern history is found.

I recently got to talk to a big-ish name in the Boston music scene, who republished one of his band's original 1985 demos after cleaning the signal up with AI. He told me that he found that tape in a bedroom drawer.

lexurco|3 months ago

I remember at one point I browsed tuhs.org in an attempt to find the source code for the original B (the language predating C) compiler. I don't think it should be in the 4th edition. I still wonder if there's a copy somewhere. I know there are a few modern implementations, but it would be interesting to look at the original.

ForOldHack|3 months ago

The 'B' compiler was written in TMG-Compiler-Compiler. TMG (Transmogrifier)

https://github.com/amakukha/tmg

https://news.ycombinator.com/item?id=26722097

""Douglas McIlroy ported TMG to an early version of Unix. According to Ken Thompson, McIlroy wrote TMG in TMG on a piece of paper and "decided to give his piece of paper his piece of paper," hand-compiling assembly language that he entered and assembled on Thompson's Unix system running on PDP-7."

We are not worthy, friends. We are not worthy."

Tons of info, but not much source:

"The first B compiler was written by Ken Thompson in the TMG language around 1969. Thompson initially used the TMG compiler to create a version of B for the PDP-7 minicomputer, which generated threaded code. The B compiler was later rewritten in BCPL and cross-compiled on a GE 635 mainframe to produce object code, which was then re-written in B itself to create a self-hosting compiler. "

So... a B compiler would use GE 635/Multics as a OS.

ekjhgkejhgk|3 months ago

OT - Mastodon is seriously cool. If you haven't yet bothered, I suggest to everyone that you spend a bit of time exploring.

fishgoesblub|3 months ago

Mastodon is just a part of the larger Fediverse.

lewiscollard|3 months ago

I was on Mastodon for three years. I deleted my account. When I found out that Charlie Kirk was murdered, my second thought was "well, best create yet another filter on Mastodon so I don't have to watch people celebrate Charlie Kirk being murdered" and when I caught myself having that thought I realised that being on Mastodon was a net negative for my wellbeing.

(I didn't like the guy either, by the way, or at least I knew enough about him that I knew I have much better things to do than listen to him. There are more than a few people like that, all of whom I wish find some peace in their hearts, and none of whom I wish to come to any harm.)

Mastodon is packed to the brim with literal psychopaths and people pretending to be psychopaths for imaginary Internet points. It is not an experience I suggest for anyone who is neither of those things.

mmooss|3 months ago

What makes it cool?

olivia-banks|3 months ago

I really, really hope data can be recovered from this. I’ve read a bunch of the original sources, and such an ancient C would be especially interesting to study.

Very proud to have had this found at my University :-)

nineteen999|3 months ago

This is amazing news for UNIX fans. Really hope the source can be recovered and put alongside the other historical UNIX source that's out there.

tgtweak|3 months ago

Very interesting storage format too - Those tapes actually held quite a bit of data (comparatively) - around 45MB (Although this one is shorter ~1000ft and probably carries about 10-15MB which is close to V4's source code, binary and documentation size).

CobrastanJorji|3 months ago

What are the odds that a medium like that has successfully stored the full data without error?

shanoaice|3 months ago

From the information I've read, quite likely, given that Utah is pretty dry. Also the original data might be stored in its uncompressed form, so even if there were some non-extensive damage it might still be possible to recover some data based upon guessing with context (if it contains text source code, otherwise if it is just the binaries then not that easy).

jonathaneunice|3 months ago

For context, I'm a geezer who got early access reading Lions' Commentary (6th Edition) and comparing it with 7th Edition source (running on a PDP-/something with no more than 128 KiB RAM). That was 1985, as Unix was spreading its way through universities. SIGSEGV haunts me to this day.

That was a full 40 years ago. And yet, 4th Edition is ancient history even to me.

pabs3|3 months ago

Hope they will upload it to archive.org and Software Heritage.

shevy-java|3 months ago

Finally we can see the naughty stuff they recorded!

lproven|3 months ago

Other posts on this subject, none with discussion:

https://news.ycombinator.com/item?id=45846438

https://news.ycombinator.com/item?id=45844876

https://news.ycombinator.com/item?id=45842643