Someone's confused

[Antonio Carlini]

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