[hatari-devel] Improving color alignment with pixels

Thomas Huth huth at users.berlios.de
Sun Dec 21 00:56:18 CET 2008

Moving this thread to the new list at berlios.de ...

On Mon, 15 Dec 2008 11:15:58 +0100 (CET)
npomarede at corp.free.fr wrote:

> On Mon, 15 Dec 2008, tobe at freemind-tobe.com wrote:
> >>> How can i adjust these timings for the blitter ? Actually a word
> >>> operation can take from 4 to 12 cycles.
> >>> The cycles buffering implemented in blitter.c was mainly done to
> >>> fix blitter-rasters, and if possible i would like to get ride of
> >>> it.
> >>
> >> in order to do this, we would need to adapt
> >> Cycles_GetCounterOnWriteAcces to have a different result depending
> >> on whether the write was made by the cpu or by the blitter.
> >>
> >> As the blitter is using iomem funtions, one solution would be to
> >> add a parameter to the functions to tell if the write is performed
> >> by the cpu or by the blitter, and use this in
> >> Cycles_GetCounterOnWriteAcces.
> >>
> >> Once this is done, we can have a case for the cpu timing and
> >> another one for the blitter.
> >>
> >> Thomas, what would be your opinion on this ?

Sounds ok for me, I also don't have a idea for a real better solution
(with good performance).

> I'm not sure a "simple bus manager" would be as simple as that. It 
> requires to break every 68000 opcodes to be able to precisely know
> when a read or a write is done in the internal micro code of each
> 68000 instruction. For example, with a "move.w (a0),(a1)" that takes
> 12 cycles, you need to know when the bus is accessed to read (a0) and
> when it's accessed to write (a1).
> This is a huge task, mainly undocumented. So far, the cpu core in
> winuae has this kind of precision, but porting it to hatari is far
> from trivial.

I once already started on a new CPU core based on WinUAE ... it's a lot
of work, but it can be done. And we would need that anyway one day, as
soon as we want to have its other new features like MMU emulation...


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