Re: [hatari-devel] TT mono mode Timer-C problem

["Roger Burrows" <rfburrows@xxxxxxxxx>]

On 22 Dec 2011 at 1:33, Eero Tamminen wrote:
> 
> On perjantai 16 joulukuu 2011, Roger Burrows wrote:
> > I was testing EmuTOS using TT mono mode (TT High), and had problems
> > opening a drive window by double-clicking on the desktop icon.
> 
> Yes, it seems to be about impossible without using Hatari's
> "middle click emulates double-click" thing.
> 
> 
> > After a
> > bit of work, I discovered that the 200Hz (5 msec) system timer is
> > actually running at about 400Hz, which (among other things), speeds up
> > the timer interrupt at etv_timer, and causes double-clicks to seem twice
> > as slow as they really are.
> > 
> > The attached program (compiled under Lattice C on a real TT) uses the
> > system ticks value in low memory to count off seconds and display them. 
> > If you run this in TT mono mode, the seconds go by at about twice the
> > normal rate.  The program also uses a crude loop counter to see if there
> > is any significant variability in the time between clock pulses (I
> > wondered if perhaps two clock pulses were being signalled every 5msec),
> > but there doesn't seem to be.
> 
> Are the counts supposed to differ between TT color and mono resolutions?
> 
No.  They are there just to see if the problem might be due to somehow taking 
two interrupts every time instead of one.  That would have shown up as a low 
count between every other interrupt, e.g.:

count 1 500000
count 2 10
count 3 500000
count 4 10
etc.

> For me they are same for both (4x times larger than for ST and 2x larger
> than for Falcon).
> 
Yes, I think that's right.

> 
> > This problem occurs with either EmuTOS or TOS 3.06, but ONLY in TT mono
> > mode. It does not occur if the screen mode is set to RGB.
> 

Roger