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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.arch
Subject: Re: time-sharing history, Privilege Levels Below User
Date: Thu, 13 Jun 2024 01:45:49 -0000 (UTC)
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On Wed, 12 Jun 2024 15:19:14 -1000, Lynn Wheeler wrote:

> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>
>> I recall CMS was single-user to start with, and the point of running it
>> under “CP” aka “VM” was to offer a multi-user service. Did CMS ever
>> become multi-user in its own right?
> 
> over years relying more & more on CP kernel services, no multi-user ...
> but did get multitasking ...

Interesting. This fits in with the idea that the “CP” in “CP/CMS” (later 
“VM/CMS”) was invented purely/primarily in order to turn a single-user OS 
into a kind-of-multi-user OS.

> trivia: my brother was regional Apple rep (largest physical area CONUS)
> and when he came into town, I could be invited to business dinners and
> argue MAC design (even before MAC announced).

So what did you think of it? The original hardware architecture was 
heavily centred around the 60.15Hz video refresh. Each refresh interval, 
21888 bytes were read out of the video buffer (for the 512×342 display), 
and 740 bytes were read out of the sound buffer to go to the speaker.

The serial controller chip, a Zilog 8530, was remarkably flexible, too. 
The third-party “MacRecorder” device involved reprogramming that to 
receive digital sound data from the external hardware microphone/dongle 
that plugged into the serial port, back before Macs had “official” sound 
input.