
Coherent OS - Jaruzel
https://en.wikipedia.org/wiki/Coherent_(operating_system)
======
EvanAnderson
Fun fact - The Mark Williams Company[1], who made Coherent, was founded by
Aaron Schwartz father, Robert Schwartz [2].

A couple of friends and I drooled over an AT&T Unix manual that our public
library had in 1990 - 1991. Unix seemed really cool but we could never afford
a real Unix machine. We talked about pooling our money and buying a copy of
Coherent but we never did. Then Linux came on the scene and Coherent was
forgotten.

[1]
[https://en.wikipedia.org/wiki/Mark_Williams_Company](https://en.wikipedia.org/wiki/Mark_Williams_Company)

[2]
[https://en.wikipedia.org/wiki/Aaron_Swartz](https://en.wikipedia.org/wiki/Aaron_Swartz)

------
wstrange
This brings back a lot of memories.

I was an intern an Inetco sytems in Vancouver (circa 1989?). They developed
switching software for ATMs that used Coherent running on Intel PCs.

My task was to extend the Coherent shell (a clone of the standard Unix sh)
with BSD csh features (history, etc.). I had nothing to go on except the csh
man page.

I have since lost the source code (it was called the "wsh"), but I suspect I
would cringe looking at it now.

Coherent was definitely my gateway drug into Unix.

------
cowmix
Coherent was a great option in and around the 1990-92 timeframe. It was a
great UNIX clone for $99 (with a great manual to boot). What killed it is
they, for some reason, spent time and treasure port XWindows to it instead of
working on a TCP/IP stack. It would have been the perfect Internet OS.

~~~
anyfoo
Just from memory, I can sort of see how they could have mistaken those
priorities. Windowing systems (with which X11 was synonymous on unixy systems)
were a big deal at the time, while TCP/IP, even networking in general, was
still emerging in what probably was Coherent's target market.

Coherent _did_ have UUCP, didn't it? In a lot of cases, that got you much
further in small to mid scale environments than TCP/IP. I wouldn't even be
surprised if Novell Netware would have been considered more important.

~~~
teh_klev
> I wouldn't even be surprised if Novell Netware would have been considered
> more important.

Speaking as a field engineer from the UK from days of yore... Up until around
1995 IPX/SPX, Novell's default networking stack at that time, was hugely
prevalent in corporate and governmental environments. I didn't start bumping
into TCP/IP in any serious way until around 1992 in my job as a field
engineer. The general kinda setup was groups of departmental Novell Netware
386 servers (I was a Netware engineer since around '87) with loads of DOS and
Windows 2/3.x clients running Novell's IPX/SPX stack atop NE2000 compatible
NIC's.

Around '95 things changed. Novell Netware 4 (as did NT 3.51 - NT done
properly) shipped and the default stack became TCP/IP...the rest is history.

~~~
Jaruzel
I think people forget how prevalent IPX/SPX and Netware was back in the late
80s-early 90s.

Fun anecdote: I used to work on a large MoD site as PC support during that
era, and one call I got was to visit a bunch of porta-cabins to fix their
Netware network because they wanted to play network DOOM and for some reason
it wasn't working.

~~~
teh_klev
Haha, this sounds familiar :)

------
tyingq
I remember the magazine ads for it:
[http://2.bp.blogspot.com/-vfzVzVxKynE/To2Hu97jlLI/AAAAAAAAAD...](http://2.bp.blogspot.com/-vfzVzVxKynE/To2Hu97jlLI/AAAAAAAAAD8/oo15jOBz0JY/s1600/Coherent+4.0+OS+32-bit+which+runs+on+80386+and+80486+machine+advert.jpg)

------
nils-m-holm
In case somebody did not know yet: Coherent is officially free software now.
You can download disk images with the whole system, including full, self-
replicting source code, here:

[https://www.autometer.de/unix4fun/coherent/ftp/vms/](https://www.autometer.de/unix4fun/coherent/ftp/vms/)

Udo's Coherent pages in general are worth a visit:

[https://www.autometer.de/unix4fun/coherent/](https://www.autometer.de/unix4fun/coherent/)

------
luismedel
I met about Coherent thanks a small article in the spanish edition of
ComputerWorld[1]. I was 13 y/o and all my computer knowledge was about Basic,
Pacal, DOS and Win3.1. Good times. I still remember the accompanying picture
in the article, showing the windowing system with an astronaut picture in a
window, some terminals and a file explorer. I think that picture inspired my
view of what operating systems should be, more than everything I've seen since
then.

Also, I recently stumbled upon Idris[2], which, as far as I know, predates
Xenix and Coherent in the PC scene.

[1] [https://www.computerworld.es/archive/omega-anuncia-
coherent-...](https://www.computerworld.es/archive/omega-anuncia-coherent-un-
clonico-de-unix-de-bajo-precio-y-facilidad-de-uso) [2]
[https://en.wikipedia.org/wiki/Idris_(operating_system)](https://en.wikipedia.org/wiki/Idris_\(operating_system\))

------
teh_klev
Back in the day (early 1991) just before Linux appeared I convinced my company
to pay for a copy of Coherent and they agreed. It was $99 and I learned a
decent amount of Unixy basics on my el-cheapo clone 386 PC. In summary it
_was_ a pretty decent learning tool. I managed to get it to connect to my ISP
and get some basic text based internet kinda things done.

I eventually filched a copy of SCO Unix from a customer (which is what I had
to support way back then - along with SCO Xenix) with a license key and ran
that for a bit and once Linux became a bit more stable (for me it was
Slackware circa 1994/1995) I started running that instead.

I kinda wonder what would have happened if MWC had open sourced Coherent back
then (provided they owned all their own code, or the third party code was
compatible with GPL/MIT/et-al)?

------
anyfoo
This is only based on playing around with it in a VM and poking at its source
code after it was open sourced with a BSD license in 2015, but to me, Coherent
seemed like a quite well put together system. Enough that it made me a bit sad
that it's now an OS of the past.

~~~
simonblack
Coherent's misfortune was that it was released at the same time that Linux
was.

All through the 90s as I progressed from Coherent to AT&T Unix to Novell's
Unixware to Sun's Solaris, I used to to look at Linux every six months or so.
I was always gobsmacked at how quickly Linux (actually Gnu/Linux) was moving
ahead in leaps and bounds.

By the time that 2001 rolled around, it was time for me to put away my Solaris
and switch to Linux fulltime.

~~~
ecksii
While Linux would have certainly killed Coherent eventually, that's not quite
the case. First Coherent was out long before Linux. Coh was around long enough
for AT&T to have sent Dennis Ritchie to Chicago to inspect the code and
evaluate it for copyright claims. Coherent ran on the PDP11 and on the 80286.
Linux became a real force in the Unix market around 1998. MWC went out of
business in Feb 1995. The first round of layoffs at MWC happened in Oct, 1994.

A perfect storm of several things killed Coherent The two biggest problems
were:

The customers dinging Mark Williams Company in the newsgroup mainly complained
about the lack of TCP/IP networking. This happened because MWC had done a
customer pole to see what big feature should come next? TCP/IP or X11. X11
won.

The real or perceived drop in quality of the product. This one is hard to
explain. Coherent 3.10 and 4.0 had been solid V7 Unix clones with V7
sensibilities. When 4.2.05 shipped it included a really nasty disk driver bug
that basically destroyed your file system beyond the ability of fsck to fix.
The bug was triggered when your drive when into a very common thermal
recalibration mode. This mode was rare or hadn't existed during the days of
MFM/RLL/ESDI drives but became common with ATA drives especially as the market
got flooded with cheap 504MB drives. While the bug was fixed somewhere between
4.2.10 and 4.2.14, the damage to Coherent's reputation was done.

~~~
nigel_bree
> The bug was triggered when your drive when into a very common thermal
> recalibration mode

As the person responsible (alas), my specific recollection of this particular
bug was that the root cause wasn't thermal recalibration, but rather UDMA
signalling errors.

Prior versions of Coherent using PIO mode had excruciatingly slow access, and
when adding support for UDMA I also added support for the disk driver to
recognise sequential access and issue multisector transfer requests; this
boosted performance fairly massively, something like 3-4 _times_ for some
common things, and it was run for a fairly long time in-house and by beta
testers with no trouble before it shipped.

The problem though, was a small - literally one line - arithmetic error when
the drive end of things reported a UDMA transfer error had occurred in the
middle of a multisector operation; the error-handling code that set up a retry
of the operation didn't compute the start kernel address correctly when a
whole bunch of transfers had been merged (and some subset had worked).

The primary problem with the UDMA modes was sensitivity to correct cable
termination - see
[https://en.wikipedia.org/wiki/Parallel_ATA#Cable_select](https://en.wikipedia.org/wiki/Parallel_ATA#Cable_select)
for some of that; basically, signal reflections from parallel ATA cable runs
that didn't have terminating resistors made things electrically marginal and
some systems would have really excessive numbers of UDMA CRC faults as a
consequence, and given sufficiently high error rates and really bad timing
that could end up polluting the buffer cache with stuff that was skewed by a
sector :-(

The big thing (on top of not having any in-house hardware that triggered this
specific bug) was the sheer volume of work required for those releases, since
getting from what was basically a fairly vanilla Seventh Edition UNIX to where
it needed to be to start running large pieces of third-party code expecting
POSIX was a big lift. Since there weren't many people, everyone was having to
wear lots of hats; for instance, aside from kernel work I did a huge amount of
work for POSIX.1 and .2 compatibility and on top of doing the underlying code
changes (which ranged all over the system, particularly for some of the stuff
we ran into Autotools scripts relying on) all of those needed documenting,
too.

[ Fred Butzen did amazing work writing the actual manpage text and making it
really easy to understand - he justly deserved the credit for the quality of
the manual in terms of its readability. But the scale of the changes needed to
bring so many parts and pieces from V7 to POSIX meant lots and lots and lots
of work trying to iterate over docs for technical accuracy at the same time as
having to redesign all the affected parts and pieces. It was, in a word,
exhausting. ]

~~~
nils-m-holm
Thank you for sharing the story! Even these days I enjoy hearing about the
company that produced the first Unix system that I used at home (Coherent
3.0). It was my main operating system for more than 10 years and, looking
back, I have never enjoyed computing more than in those days.

Regarding the driver bug, I guess I was lucky, because I still used a MR-535
MFM disk in the late 1990's. I think I later upgraded to a 100MB IDE disk, but
was still lucky.

Personally I was not even happy about the move from V7 to POSIX, because I
enjoyed the simplicity of V7 very much, but things started to change and
supporting POSIX was certainly a neccessity at that time.

Anyway, thanks for contributing to a great OS! I still keep a VM with 3.2
around and use it regularly.

~~~
nigel_bree
> I think I later upgraded to a 100MB IDE disk, but was still lucky.

Well, it really wasn't luck as much as keeping with the electrical specs. Do
that, you'd never see a problem, and the later IDE "cable select" schemes did
really help to mitigate a lot of the damage from improperly terminated cables.

> Anyway, thanks for contributing to a great OS!

Well, other than living in infamy due to introducing that bug, I didn't start
there until the push to turn 4.0 from a tech demo into a real product. So
really all the credit for 3.2 and earlier which set the foundation for
Coherent belongs to the other guys, many of whom were long gone by the time I
got there like Dave Conroy (who wrote the MicroEMACS I loved to use) and
Randall Howard (who went on to found MKS). There were some great people from
the earlier days still there though, like Norm Bartek, Hal Snyder and La Monte
Yarroll who where there when I joined and of course Steve Ness who was the
sole man behind the MWC C Compiler (much as Fred was responsible for that
remarkable manual).

Also worth a mention, among all the other notable characters I remember fondly
is one of the support/QA folks at MWC: Jim Leonard aka Trixter, who became a
notable demoscene figure - [https://trixter.oldskool.org/2015/04/07/8088-mph-
we-break-al...](https://trixter.oldskool.org/2015/04/07/8088-mph-we-break-all-
your-emulators/)

------
tass
My dad (or maybe his work) bought Coherent for him to learn UNIX and we had a
setup in the garage with serially-connected VT100-like terminals.

It was my only time knowingly using a UNIX-like OS until a few years later
when I installed Slackware.

------
Mountain_Skies
Almost bought it after seeing the stunningly low price. $99 for a Unix like
OS? It seemed too good to be true. At the time my housemate and I ran a small
multiline BBS we wanted to make into something bigger. Coherent would have
been to run Picospan after seeing how well M-Net worked. Someone we contacted
at the Mark Williams Company said they didn't think Picospan would work with
Coherent's memory model. No idea if that was correct but we went with MajorBBS
instead for our big upgrade. Still thought about buying it to play with but
Linux showed up before I had the spare money for Coherent.

------
simonblack
Coherent was my entrance to the wonderful world of Unix back in 1991. Thanks
to Coherent's introduction I never ever had to endure Windows as my everyday
personal desktop environment.

------
MarkMMullin
Ran this on the Ithaca Intersystems Z-8000 based rig in the early/mid '80s -
it was remarkably command compatible with V7 for the basics, even built a
MicroAngelo based 3D graphics system on it.....the biggest problem the box had
wasn't Coherent, it was the fact the socketed logic on the custom MMU S100
card kept trying to walk out of the sockets because of thermal issues

------
nineteen999
These days (as another poster has already pointed out) it is under an Open
Source license.

The author of this page:

[https://www.autometer.de/unix4fun/coherent/index.html](https://www.autometer.de/unix4fun/coherent/index.html)

previously worked for MWC and has put some quite detailed notes on setting up
various aspects of Coherent running under Virtualbox there.

------
icedchai
I ran this on a 386SX for while in 1991. It came with a very comprehensive
"Unix" manual. A couple years later I switched to Linux...

------
_bxg1
Did Linux deal with any of the same legal scrutiny?

~~~
hobo_mark
Yes, for years...

[https://en.m.wikipedia.org/wiki/SCO–Linux_disputes](https://en.m.wikipedia.org/wiki/SCO–Linux_disputes)

~~~
msla
SCO was a farce. Microsoft used a company called BayStar to fund SCO's
lawsuits, which had absolutely nothing to them; SCO wouldn't even _release_
the evidence it claimed to have proving code copying for a suspiciously long
period of time, and when the evidence was released, it was nothing of the
sort. Ultimately, the legal merits of the case wouldn't have mattered, in that
a bad lawsuit can still drown an opponent. What mattered was that Microsoft
waited too damn long to try it: One of the players on the other side was IBM,
which by then had a serious business in Linux on mainframes, and a two-bit
nuisance suit jumped up with some venture capital wasn't going to sink the
damn Nazgul.

[https://www.computerworld.com/article/2547289/baystar-
exec-s...](https://www.computerworld.com/article/2547289/baystar-exec-says-
microsoft--guaranteed--sco-investment.html)

~~~
macspoofing
>Microsoft used a company called BayStar to fund SCO's lawsuits

Your article suggests otherwise. It seems like some over-eager Microsoft exec
promised that BayStar's investment would be 'guaranteed' by Microsoft. That
exec was subsequently fired and nothing was formalized. BayStar ultimately
lost money on SCO. But even that much is suspect as this account is hearsay
and comes from a managing member of BayStar who has cause to deflect blame for
his or his company's dumb investment in SCO.

~~~
fulafel
MS claimed to have changed their minds, but it's hard to say what really went
on there. Due to the nature of the whole enterprise people would be very
conscious of what to put on paper / email. It seems plausible that the SVP was
just paid a lot of money to quit and not refute the blame placed on him after
the rest of MS decided to wash their hands.

(And in any event, actions by the responsible executives are actions of the
company, and going back to say "it was just this guy, not MS the company" is
not really the right way to think about it)

~~~
macspoofing
Again, you're taking the words of a BayStar managing member at face value.
Why? He has a reason to lie and deflect blame. There is no other supporting
evidence.

Nothing else rings true about his story either. Like for example, you don't
make a big investment as private equity firm based on flimsy (at best)
guarantees. Regardless, had that guarantee actually happened and BayStar
really believed it, they would have sued Microsoft just to embarrass them and
force a settlement.

I'm sure Microsoft was applauding the lawsuit but that doesn't mean they
funded it as OP just outright stated.

> It seems plausible that the SVP was just paid a lot of money to quit and not
> refute the blame placed on him after the rest of MS decided to wash their
> hands.

Only if you're conspiratorial minded because that doesn't seem plausible at
all.

I think your dislike of Microsoft clouds your judgment.

------
Foroldhack44
in 1990, while working for an insurance company, we were looking for what UNIX
to port a multi user database to, We looked at SCO, Microport, Cohernet and
Sperry. The company chose Microport, and the Sperry went back, so I got to
keep SCO and Coherent. Loaded and ran both, liked SCO a tiny bit more because
of it successfully compiling a few programs, and heard about the UNIX
Copyright controversy.

Coherent installed, and ran, but had a few incompatibilities with our
software, but ran solid as hell. The documentation was very good too.

------
bifrost
I remember using Coherent along with Xenix around the same time. I think I
tried everything I could get my hands on :) I even used 386BSD heh.

