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From: Lynn Wheeler <lynn@garlic.com>
Newsgroups: comp.arch
Subject: Re: ancient OS history, ARM is sort of channeling the IBM 360
Date: Sun, 30 Jun 2024 09:09:23 -1000
Organization: Wheeler&Wheeler
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jgd@cix.co.uk (John Dallman) writes:
> Are you sure? Per Wikipedia, the lowest-end real S/360, the Model 30,
> could run with only card equipment, running BPS, or with only tape drives,
> under TOS. 
>
> <https://en.wikipedia.org/wiki/IBM_System/360_Model_30#System_software>
>
> BOS was a really minimal OS for an 8KB RAM machine with one disc drive,
> and DOS was less minimal. 
>
> The Model 30 was apparently one of the most popular machines in the early
> days of S/360. Being able to build such small machines was a strong
> commercial consideration for the company, and thus the architecture. 

at end of semester after taking two credit hr into course, was hired to
rewrite 1401 MPIO for (64kbyte) 360/30 ... which was running early
os/360 PCP (single executable program at a time) ... had 2311 disks,
tapes, and unit record. I first had a 2000 card program, assembled under
os/360 but ran "stand-alone" ... being loaded with the "BPS" loader (had
my own monitor, device drivers, interrupt handlers, error recovery,
storage management, etc. Making changes during development & test
required brining up os/360 and re-assembly and then stand-alone loading.

I eventually got around to adding os/360 mode of operation using
assembly option to generate either the stand-alone version or the os/360
version. It turns out the stand-alone version took 30mins to assemble,
however the OS/360 version took an hour to assemble (OS/360 required DCB
macro for each device and each DCB macro added six minutes elapsed time
to assembly) ... aka stand-alone testing and then re-ipl for OS/360
30min re-assemble still took less time than OS/360 testing and hour
re-assemble.

-- 
virtualization experience starting Jan1968, online at home since Mar1970