6 May
2016
6 May
'16
10:48 a.m.
I've always wanted to know more about the SDS 940 project since its a
relative to my SDS Sigma 9. If you know of any of the papers on the
hardware, and OS they created I'd appreciate some pointers to where I could
read them. Thanks!
On Wed, May 4, 2016 at 2:00 PM, Mark Kahrs <mark.kahrs at gmail.com> wrote:
Al mentioned the 940 so I thought I would fill in the
details:
Lichtenberger and Pirtle extended the hardware to include a page map: 14
bits of VA was divided into 3 bits of page # and 11 bits of offset. The 8
pages were held in 2 x 24 bit words divided into a 8 x 6 bit page numbers.
The high order bit of the mapped page number served as the Read Only bit.
This meant that "subsystems" (a.k.a. applications) could be shared between
users.
Additionally, the instruction set was protected against users with specific
prohibition against using the I/O instructions.
This was described in FJCC 1965 with modifications done in 1964.