Re: IBM and Amdahl history (Re: What is an N-bit machine?)

In article <2024Nov30.191907@mips.complang.tuwien.ac.at>,
anton@mips.complang.tuwien.ac.at (Anton Ertl) wrote:

An overview of what is still going on in the mainframe business is
<https://arcanesciences.com/os2200/app1.html>.

There's one bit that's puzzling:

| Hitachi, though they once had a thriving global business including
| North America, markets their systems exclusively in Japan. Until
| approximately 2020, they built custom CPUs, but in the latest
| generation - the AP10000 - they rebadge IBM Z running their own
| MVS-derived VOS3 operating system. I'd guess they have 200-300
| sites, almost all in Japan.

If Wikipedia is correct, Hitachi did not extend VOS3 to 64-bit:
<https://en.wikipedia.org/wiki/MVS#Closely_related_operating_systems>

Wikipedia also says that the 2015 models of IBM Z machines are the last
that can run 31-bit operating systems:
<https://en.wikipedia.org/wiki/IBM_Z#IBM_z13>

It seems like one of these must be wrong, but I don't know which.

Another interesting comparison is VMS Software Inc. (VSI), which
took over the VMS legacy in 2015.  They are "150+ collegues" and
have "2K clients"; Unisys have fewer MCP and OS2200 clients
according to the site above, but Unisys had 16300 employees in
2021.  Maybe the mainframe clients of Unisys need a bigger
support force than the VSI clients, or maybe the Unisys employees
mostly work on other things.

I've had a little contact with VSI. They /only/ do VMS, which isn't
terribly arcane: a 32/64-bit OS that uses ASCII on twos-complement
little-endian hardware. It's been ported to x86-64, and that's being
adopted by customers.

Unisys staff do all kinds of things, and their mainframe OSes are much
less mainstream than VMS.

John