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 anto...@acarlini.com
