Re: DeskNC Windows version

--- In CAD_CAM_EDM_DRO@y..., beer@s... wrote:
> On 19 Apr, CAD_CAM_EDM_DRO@y... wrote:
>
> > I haven't looked into Linux and it's interrupt rates, but the way
I would do
> > it is reprogram the hardware timer on the system board to a much
higher rate
> > then add your own interrupt service routine to divide down the
faster tick
> > rate back to the original rate for routines that depend on it.
>
> Believe it or not, the original IBM programmer's reference for the
> IBMPC circa 1981 showed how to do exactly that - even recommending
it
> as a technique.
>
>
> > That's the trick we used to do on DOS to get high interrupt
rates. Then trap
> > INT 08 if memory serves.
>
> I've frequently been lazy and NOT trapped the interrupt, the result
> being the time is WAY OFF by the end of the program.
>
>
> > I'm not sure what the minimum resolution was but it seems like it
was around
> > .8 us.
>
> Now I'm getting fuzzy, but I think it's 14.318 MHz / 16 for just
over a
> one uS minimum period.
>
> 14.318 also divides nicely to 3.58, the colour burst frequency for
NTSC
> video, which is why it was used.
>
> Strange, what we're talking about today in terms of timing pulse
> limitations comes about as a result of an IBM design decision in
> 1979/80.
>
> ( to make a machine that could display its output on a conventional
TV
> AND to put that hardware on the motherboard and not on the display
> adapter card AND to then use THAT crystal as a reference for most
> other timings AND to use off the shelf Intel support chips.)
>
>
>
> Alan
>
> --
>
> Alan Rothenbush | The Spartans do not ask the number
of the
> Academic Computing Services | enemy, only where they are.
> Simon Fraser University |
> Burnaby, B.C., Canada | Agix of
Sparta