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Typical Data Bandwidth to VDP During VBlank
Posted: Mon Oct 06, 2014 12:12 pm
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Does anyone have good figures on what VDP transfer rates a tight assembly loop can achieve during VBlank?
I have a crazy idea... |
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Posted: Mon Oct 06, 2014 5:22 pm |
http://www.smspower.org/forums/viewtopic.php?t=14599
You can do a lot better if it's not coming via the Z80, and slightly better if you don't need to read data from memory. |
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Posted: Mon Oct 06, 2014 9:57 pm |
It would be cool to see a DMA device that could read from the fast on-cart flash, and write it to the VDP quickly within the timing limitations. | |
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Posted: Tue Oct 07, 2014 3:25 am |
N*nt&nD@ had support chips; we can do it too! We can do it better! Haha! No that wasn't my idea but still that would be pretty cool! |
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Posted: Tue Oct 07, 2014 5:41 am |
I read about the Graphic Board, and discussion of graphics limitations and realized the NES had a drawing app that let it (very slowly) draw a fullscreen bitmap (using a standard controller), but then I recall the reason even that was possible: because the NES required the tile memory to be present on the cart (rather than built in the console, like probably every other console ever created :D ) it was possible to expand the memory (though still subject to all the other limitations like number of colors).
I'd guess no such luck on MS? |
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Posted: Tue Oct 07, 2014 7:24 am |
Correct. In theory you could try to write to tiles that had already been displayed and reuse them later, but that still doesn't get you anywhere near enough tiles. You could use the legacy video modes but the disadvantages are quite severe. | |
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Posted: Tue Oct 07, 2014 7:58 am |
Bitmap is indeed possible, if you don't do it fullscreen... | |
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Posted: Tue Oct 07, 2014 8:52 am |
TmEE is working on such a device. I cannot post a link but have a look on Sega 16 in the thread about reverse engineering the 6502. |
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Posted: Tue Oct 07, 2014 1:32 pm |
Haha - yeah!!! Theoretically, could we even have a cartridge-based VDP upgrade to overcome lets say sprite limitations (8 on a scanline)? |
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Posted: Tue Oct 07, 2014 1:39 pm |
You mean replace the VDP functionality with a new chip in the cart? I don't think so... and expand internal VDP hardware sprite limit I guess it's really impossible. | |
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Posted: Tue Oct 07, 2014 2:19 pm |
Why not implement a video chip that does overlays, then loop the host system video through... may as well put a faster CPU and more RAM in there too... let's call it a "32X"? | |
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Posted: Tue Oct 07, 2014 2:30 pm |
Then let's not develop but few titles for it... | |
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Posted: Tue Oct 07, 2014 3:35 pm |
Haha, I foresaw some witty comments here :) lets not forget that this thread is about VDP and "a crazy idea...".
I get the point, though. On a micro level I had these thoughts when building the arcade table: Not only the internal hardware, but also the old peripherals, are part of the SMS experience, in all its limitations and glory. |
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Posted: Fri Oct 10, 2014 4:27 pm |
Yes I completely agree, limitations are definitely part of the experience! I'm studying different applications and upgrades for my Power Base Converter series. |
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