8 Jun
2020
8 Jun
'20
3:40 p.m.
On 08/06/2020 21:54, Chuck Guzis via cctalk wrote:
Although there are exceptions. I recall that it was
possible, using
large page sizes on the CDC STAR-100 to execute an instruction that
could never get started. The STAR had 512KW (64 bits) of memory and a
large page size was 64KW. A typical vector instruction could require 6
addresses for source, destination and control vectors. Put the starting
address of any of these in last 8 words of a page and the hardware
faulted preemptively for next page. It was kind of funny to watch; the
P-counter for the user never budged, but the pager was sucking up time
like crazy. I think someone eventually devised a check in the pager for
this case, but I'm not certain.
There was a standard VAX quiz question which was something along the
lines of "what's the largest number of page faults can a single (valid)
instruction cause" and the answer was surprisingly large (in the region
of 50+ although I can no longer remember the details.
Antonio
--
Antonio Carlini
antonio at acarlini.com