| glen herrmannsfeldt 2006-01-18, 3:55 am |
| multicsfan wrote:
> The 360/91 wasn't the only one with problems. When I played with the
> Watfiv source there were comments here and there about problems
> different model 360's had. Some were in error trapping. I don't
> remember which model(s) (I still have the printed source), but some of
> them wiht pipelines could not accuratly report what instruction caused
> an error, just that it was one of the ones in the pipe that caused the
> problem.
> I believe some other early pipelined machines had this problem or even
> worse ones. not only did they have problems with error tracing during
> execution but sometimes the program counter wasn't properly tracked
> during normal interrupts like I/O, timers, etc.
Imprecise interrupts.
Some other processors had imprecise interrupts for things like
protection, but the 360/91 and /195 had them for many of the floating
point operations. With out of order execution and completion, it
must complete all instructions before the interrupt can be taken.
PL/I (F) has a message that changes when sysgenned for the 91,
such that messages say NEAR when indicating where the error occurred.
Though with the STMT option it will put BR 0 instructions between each
statement to flush the pipeline. (And slow everything down.)
-- glen
|