Re: Timing problems

[Clarence Dang <clarencedang@yahoo.com>]

On Tuesday 26 June 2007 11:33, John Coppens wrote:
> On Fri, 22 Jun 2007 17:40:42 +1000
>
> Clarence Dang <clarencedang@yahoo.com> wrote:
> > On Wednesday 20 June 2007 15:08, John Coppens wrote:
> > > I suspect this program uses the DOS 18.xxx Hz timer for its loops. Is
> > > the emulation of the timer under DOSEMU the same frequency? Does it
> > > depend on setting up the 250/1000 tick/s of the kernel?
> >
> > DOSEMU can handle about 100 Hz for the PIT.
> >
> > I have a patch I can dig up that can go up to 250 (or even 1000
> > depending on the kernel version).  It's just a quick hack and not the
> > proper solution though.
>
> In reality, the problem is the other way around - I have the impression
> that DOSEMU is using anything but 18.29 Hz. At least the program is not
> responding the same way under DOSEMU as in real DOS, which causes the
> login sequence to fail.

Internally, DOSEMU is ticking at 100Hz 
[src/base/init/init.c:timer_interrupt_init()] but from a DOS program's point 
of view, it will correctly appear to be whatever the emulated PIT is set to 
(e.g. 18.2Hz).  Emulation of anything less than 100Hz should be fine.

> It's rather strange really - using the normal serial port, I get one kind
> of behaviour, and using an USB to serial converter, DOSEMU responds
> completely differently (none of them correct). I'm somewhat at a loss
> where to look for solutions here...

Maybe setting $_hogthreshold to 0 will help (lets DOSEMU use as much CPU as it 
likes).