history is hard

Eric Smith spacewar at gmail.com
Sun May 31 01:15:40 CDT 2020

On Fri, May 29, 2020 at 3:30 PM Jon Elson via cctalk <cctalk at classiccmp.org>

> On 05/29/2020 02:38 PM, Noel Chiappa via cctalk wrote:
> >      > From: Jon Elson
> >
> >      > As far as I know, there was no VM/360. There WAS VM/370, which
> was out
> >      > in the early 1970's
> >
> > CP/67, which was a semi-product, and ran only on 360/67's, was basically
> the
> > same functionality as VM/370. (I get the impression that the code was
> > descended from CP/67, but I can't absolutely confirm that
> I think it was, too.  But, only a /67 could run this.  Any
> other 360 would have big security/reliability problems if
> they tried to implement this kind of virtualization.
> Low-level machines did not even have storage protection
> keys, and on the /40 and /50 (I think) it was an option,
> although I'd guess almost any /50 had it installed.  And,
> the storage protection keys were a very coarse/crude tool,
> although you could set up
> sharable read-only areas.

The issue wasn't whether the machine had storage keys (protection, SSK and
ISK instructions). AFAIK CP/67 didn't use that even when available. What
CP/67 and VM/370 required was Dynamic Address Translation (DAT), and the
360/67 was the ONLY 360 model for which that was available. Contrary to
popular belief, DAT wasn't even available on every 370 model, as it was an
optional feature of the 370 architecture.

CP/40 was developed on a modified 360/40 that had DAT (with the addition of
a "CAT box"), but was never available as a product.

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