[Simh] Losing Time In SIMH

[Paul Koning]

> On Jan 31, 2017, at 3:07 PM, Mark Pizzolato <Mark at infocomm.com> wrote:
> 
> ...
> Simh tracks and adjusts for wall clock behaviors quite reliably.  The problem here
> is that the OS is programming the interval timer device to generate ticks at 60Hz
> and we don't have other common examples that do this on the VAX.  It seems
> like it is programming the interval timer register to -16667, and ticks per second
> is being computed to be 100000/16667 which ends up to be 59 rather than
> 60.  This causes the very consistent calibration at 59Hz and therefore the timing
> results he is seeing. 

But 1000000/16667 is not 59, it is 59.9988.  Does SIMH actually deliver 59.0000 Hz for that setting?  That would certainly cause trouble.

	paul