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DanBoris

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  1. I will have to look into that one. My assumption is the "corruption" that occurs when you overlap characters is predictable so certain interactions may be useful. Someone actually created a utility to figure this sort of thing out. http://www.guttenbrunner.com/videopac/
  2. If two characters are touching, even if the pixels are blank, it will mess up the character graphic. I would like to play around with that interaction some more to see if I can figure out how the VDC hardware handles this and maybe even find a way to emulate it. Internally graphics data has to move into a shift register so it can get clocked out onto the screen one pixel at a time. Since sprites can overlap each other, there is likely one shift register for each sprite. With the characters, my assumption is that there is a single shift register that is why characters cannot overlap.
  3. Sprite and characters are different things. Sprites have a user definable shape and can overlap any other object on the screen, sprite of characters. Characters have to come from the internal character set and can not overlap other characters. The O2 clearly wasn't "dead on arrival" since it has a good sized library of decent games. It was not as flexible as the 2600 but the programmers managed to do some cool stuff with the hardware. The Channel F did have more flexible graphics, but it O2 had a higher resolution and a little more color flexibility. The Channel F also has a pure bit-mapped display so the CPU had to do all the drawing work which would have made if difficult to go more complex arcade style games like the O2 did.
  4. I did verify on the actual hardware that if two characters overlap, even overlapping blank pixels, you get strange results. Here is a picture of what happens when I try to put two character 27s right next to each other. You can see one on the left but the other becomes garbage.
  5. Yes, but you can re-use a sprite as you go down the screen so you can have more the 4 moving sprite objects.
  6. There are only four 8x8, one color sprites. You could stretch them by reusing the down the screen, but you couldn't have more then four on a single line.
  7. Sprite shapes are custom defined, they don't come from the internal character set.
  8. I am not the author but I assume they are just sprites.
  9. No, this is not true. The chip that does the audio and video was custom designed by Intel for Magnavox. Good article about that here: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=5223987
  10. Adding a bit mapped mode would have required a lot of extra RAM which was very expensive at the time.
  11. It's easy to say this in hindsight, but at the time their design decision probably made more sense. This system went into development in probably early 1977 if not late 1976. The console industry, including Magnavox's own products, was all dedicated consoles playing pretty simple games and the 2600 was still close to a year away from release. The O2 even with it's limitations, was a major leap forward for their product line.
  12. This is definitely not a production unit. The board is made by General Instruments who made the voice synth chips. The production unit used serial ROMs for the voice data which would be difficult to use during development, so this board allows you to use stock EPROMS instead. Games could also contain additional voice roms in the cartridge so this may be been used to develop new voice games.
  13. I really need to get my O2 development system set back up so I can test some of these ideas.
  14. You might be able to change the image from scanline to scanline, but it's unlikely you could change it on a single line. The hardware probably works by loading the bit pattern for each character line into a shift register which is then shifted out into the video signal. If that is the case then once the character has started to be drawn you wouldn't be able to change it.
  15. The board with the ROMS has pretty much all the voice circuitry. The SP0256 is the voice synthesize chip, and the ROMS hold the voice data. The other large is a parallel to serial converter which is needed to convert the eprom data into a serial interface that the SP0256 uses. The production version uses serial ROMS so doesn't need that chip and takes up less space. The other board in the case appears to be a voltage regulator that is being used to power the voice board. The only thing that is missing is the audio amplifier. If the PCB is still in the voice module it might be using the one in there.
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