Why VGA and not DVI/HDMI


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robert.rozee
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Joined: 31/12/2012
Location: New Zealand
Posts: 1991
Posted: 12:14pm 22 Jan 2022      

  lew247 said  you can drive DVI-D video through and using the board DVI goes up to 720p


it is pretty impressive  

however, it looks like he may be doing pixel-doubling in both horizontal and vertical directions, simply to fit within the available RAM.

we have just over 256k of RAM available. ways of slicing-and-dicing this include:
720p: 1280 x 720 -> 2-bits per pixel (black + 3 distinct colours), 20k left over
720p: 640 x 360  -> 8-bits per pixel (RR-GGG-BB), 20k or so left over
640x480    -> 4-bits per pixel, with around 100k left over

this doesn't seem that much more impressive that what peter is already getting out of a VGA connection; 2bpp will look awful, think ZX spectrum colour rendition. this does not make for a great 'games experience'.

for text, 640x360, displayed on a wide-screen monitor gives 80x24 text with a character cell of 8 pixels wide x 15 pixels high. now this is almost interesting, giving you a nice terminal screen if you can find a font that will render well with just 7 pixels of width (1 pixel lost between each character).

while i like the idea of 2x pico's coupled together (one as display driver, the other for MMbasic), cost wise the economics become pretty tight: 2x pico + DVI socket and PCB, versus, cost of a RPI zero W2 (which has onboard DVI, + USB keyboard support to boot).

i have great faith in Tom's MMB4L port, which will, ultimately, produce a "micromite" with (essentially) unlimited RAM running at phenomenal speed. current list price of a RPi zero W2 is just nz$25.


having said all this, the DVI hack is very cool  


cheers,
rob   :-)
Edited 2022-01-22 22:15 by robert.rozee