18 Jan
2007
18 Jan
'07
8:15 a.m.
On 1/18/07, Don North <ak6dn at mindspring.com> wrote:
A few years earlier Apollo Computer came out with
their first system
that employed a 68000 that implemented a full demand paged virtual
memory system. The trick they used was to have two separate 68000
processors, one for the user and the other to service page faults.
When it was determined that the user processor would fault, that
68000 was frozen mid-access, then the system 68000 would service the
fault, fix memory up, and then let the user 68000 continue. Actually
kind of an innovative approach at the time.
I don't know who did it first, but in the mid-1980s, I worked with a
Perkin-Elmer workstation (can't recall the exact model number (7xxx?),
running System III, ISTR) with a similar coupled 68000 page fault
scheme.
It was not a new box in 1985 when I first saw it. One distinct
feature - it had several (10?) buttons built into the lower bezel on
the console CRT that were referred to as "soft function keys". There
was some way to twiddle the bottom line of text on the console to
"label" the buttons, but we never used them. We mostly used the box
as a C->68K assembler engine to feed a home-grown assembler to make
embedded product images, but that has nothing to do with page demand
VM. ;-)
The 68010 came out a short time later, making all this effort a
historical footnote.
-ethan