On Fri, 11 Dec 1998, Nigel Goodwin wrote:

> to get anything like that accuracy. Now 78uS is a totally different
> game, I suspect that would be MUCH! harder still - I wouldn't even like
> to try from DOS, across a broad speed range of machines - if it was only
> to run on one specific machine DOS would be easy :-).

Actually I did that from DOS, I added a 'dummy' flag to the IO routine and
ran it in 'dummy' until a second ticked, then ticked again, this gave a
calibration figure at run time. Then I displayed a message telling users
to stay away from the Turbo button, and used the calibartion value to
insert dummy cycles as required when doing IO during programming.

I suppose that the only thing that might make a 70 usec delay under
Windows possible, would be a boot virus that adds itself to the API
somehow (in cooperation with a VxD that you write probably ).

It is just barely possible that one could write an assembly VxD that takes
over complete control for 70 usec. I have never tried this.

Peter