jltursan escribió:Pere, apoyo esa moción acerca del "PMODE316"
. Si ya me gusta el VG6, ese otro ya sería la caña (siempre que nos dejaran usar paletas). Para empezar nos traeríamos los juegos de CPC así por la cara
Mira, como sigo cruzándome correos con ambos, Ed y Brendan, acabo de recibir hace un cuarto de hora dios respuestas suyas que, un pelín a
traición, las voy a incluir aquí. Están en inglés, y encima contienen explicaciones técnicas complicadillas ...
----- De Brendan Donahe --------------------------------------------------------------------------------------------------------------------------------------------
Pere,
There are 2 6kB buffers in CoCoVGA so that one can be written by the CPU while the other is being displayed on the VGA output. This is to avoid "tearing" since the VGA refresh rate is faster than the 6847's refresh rate. (That is, on-screen objects that are in motion may sometimes have the upper part of them in the current frame and the bottom part of them shifted in some direction in the next frame.)
What you describe might be possible if we switch the SAM to alternate between 2 different (probably adjacent) 6kB video RAM windows during
each vertical blanking period providing a total of 12kB. Obviously, this would require FPGA changes, as well. If this is something very desirable,
I can start to look into it, although I'm not sure how quickly I'll be able to get it done. Because it is yet another addressing mode of these buffers
and that is already a logic speed path, I may have to rework the video pipeline, but that is something I'm considering for sprites anyway.
Certainly, there is the risk that we would see the tearing that I'm trying to avoid. Is 128x192 16 color mode still desirable if there is some tearing?
One other option to consider is to take advantage of CoCoVGA's ability to alter the colors from the stock Dragon/CoCo color set, either in PMODE3
or PMODE4. MESS artifact mode in PMODE4 has a way to display up to 16 colors, although it's far from ideal since it takes horizontal pixel position
and position relative to other set/cleared pixels in the row into account. There is also a less useful SmArtifact mode available in PMODE4 which I believe displays up to 8 colors.
Thanks,
Brendan
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No se si nos conviene tanta complicación para acabar con imágenes compuestas de dos frames distintas, peor que flickering!
Y Brendan está estudiando dar soporte hardware a sprites esto si sería grande!!
------Y ahora el de Ed Snider -----------------------------------------------------------------------------------------------------------------------------------------------
Hi Pere,
The only thing I can think of that may be possible without changing theCoCoVGA hardware itself is the possibility of using the SAM’s DMAmode.
I briefly looked at this and it seems as if we might be able to get 12K pages to work for a new video mode (keeping things at 60fps).
I’m not sure if the FPGA has a enough resources left though, it may require a redesign of the board to go any further.
- Ed
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Esto sería bastante mas interesante pero podría ser que la FPGA usada en el módulo está ya muy llena y no queden células suficientes para implementar el nuevo modo
saludos
pere