Given the number of ex-MTS (Bill Joy and Ted Kowalski, to name two) and TSS hackers that were also later to be UNIX hackers after their original introduction to system programming as undergrads.  I will keep this reply in TUHS, although it could be argued that it belongs in COFF.

Note good sources for even more of the background of the history politics at both IBM & GE can be found in Haigh and Ceruzzi's book: "A New History of Modern Computing" - which I have previously mentioned as it is a beautiful read.

On Fri, Dec 16, 2022 at 5:27 PM Douglas McIlroy <douglas.mcilroy@dartmouth.edu> wrote:

IBM revealed Gerrit Blaauw's skunk-works project, the 360/67,
but by then the die had been cast. Michigan bought one and built a
nice time-sharing system that was running well before Multics.

All true, but a few details are glossed over, and thus, this could be misinterpreted - so I'm going to add those as one of the people.

TSS and the /67 was IBM's answer to Multics, as Doug mentions.  Note that the /67 could run as a model /65, which as I understand it, most of the ones IBM sold did. 

At the time, IBM offered the /67 to Universities at a substantial discount (I believe even less than the /65).  Thus, several schools bought them with Michigan, CMU, Cornell, and Princeton that I am aware of; but I suspect there were others.

TSS was late, and the first releases could have been more stable.   Cornell and Princeton chose to run their systems as /65 using the original IBM OS.  CMU and Michigan both received copies of TSS with their systems.   Michigan would do a substantial rewrite, which was different enough that became the new system MTS.   CMU did a great deal of bug fixing, which went back to IBM, and they chose to run TSS.  [I believe that CMU runs OS/360 by data and TSS at night until they felt they could trust it to not crash].  Nominally, TSS and MTS should share programs, and with some work, both could import source programs from OS/360 [My first paid programming job was helping to rewrite York/APL from OS/360 to run on TSS].  So the compilers and many tools for all three were common.

MTS and TSS used the same file system structure, or it was close enough that tools were shared.  I don't know if OS/360 could read TSS disk packs - I would have suspected, although the common media of the day was 1/2" mag tape.

This leads to a UNIX legacy that ...  Ted's fsck(8) - which purists know as a different name in the first version -  was modeled after the disk scavenger program from TSS and MTS.   icheck/ncheck et al. seem pretty primitive if you had used to see the other as a system programmer first.   Also, a big reason why all the errors were originally in uppercase was the IBM program had done it.  In many ways, neither Ted nor I knew any better at the time.

Clem