According to Scott Lurndal <slp53@pacbell.net>:

I was there and not really. On the 11/45 and 11/70 you got 64K of

I was there using v6 on an 11/34. Granted, never had a chance
to use the 11/70, but heavily used the 11/780 (loved it!). Our
11/44 ran custom software acting as a terminal controller.

instruction space and 64K of data space. The hardware divided each
into eight 8K pages but they were too big to be useful so each segment
was always contiguous and could be from 8K to 64K in 8K increments.

At Yale we had an 11/45 with an aftermarket cache that made it nearly
as fast as an 11/70. We also built some of the first bitmapped
terminals, using giant state of the art 2K RAMs. There were 16
terminals each with 32K bytes of memory that could be mapped into both
the 11/45's address space and an adjacent 11/05 that ran a terminal
emulator. The first thing I did was to let you map your terminal
memory into the top half of the data space which was fast but losing
half of your address space was painful.

Then I noticed that the 11/45 had a third supervisor mode intended
between user and kernel with its own address space. Unix didn't use
it, so I mapped the screen memory into supervisor space, set the
program status so that for user programs the supervisor was the
"previous" mode, and then could use hardware move to/from previous
space instructions. The C compiler didn't generate those so we had
some little assembler routines to manage screen memory. It worked
great, the undergrads wasted tons of time writing screen hackery.

--
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly

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