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Arcade Lifestyle / Re: And now for something else: NES RGB mod
« on: July 14, 2015, 04:52:52 AM »
technical background on NESRGB:
- the NES PPU chip only outputs composite video (Playchoice-10 is the only PPU that has RGB out, but the color pallet is not the same as NES, some games have slightly different colors. e.g. brown where it's supposed to be more red).
- the FPGA on NESRGB sits between CPU and PPU and intercepts writes to PPU
- it forces PPU to output most of the digital data (color vectors) on the PPU's EXP pins (these pins are normally connected to ground!)
- only missing data is if color belongs to foreground, or background. To force that data out of PPU, the FPGA will force picture to black and white palettes. Then analyze output from composite video which will tell it if the color was foreground or background!
Now NESRGB has all the info it requires (color and sync information) in pure RGB. It can then output the RGB, or convert it internally to S-Video or composite which is much cleaner than the old NES PCB which has a lot of added noise.
It was a huge breakthrough that occurred on NESDEV back in 2013. It was Tim W. who made the NESRGB the commercial success it has become. If this wasn't for this work, a lot more PC10 systems would be killed for its RGB PPU.
- the NES PPU chip only outputs composite video (Playchoice-10 is the only PPU that has RGB out, but the color pallet is not the same as NES, some games have slightly different colors. e.g. brown where it's supposed to be more red).
- the FPGA on NESRGB sits between CPU and PPU and intercepts writes to PPU
- it forces PPU to output most of the digital data (color vectors) on the PPU's EXP pins (these pins are normally connected to ground!)
- only missing data is if color belongs to foreground, or background. To force that data out of PPU, the FPGA will force picture to black and white palettes. Then analyze output from composite video which will tell it if the color was foreground or background!
Now NESRGB has all the info it requires (color and sync information) in pure RGB. It can then output the RGB, or convert it internally to S-Video or composite which is much cleaner than the old NES PCB which has a lot of added noise.
It was a huge breakthrough that occurred on NESDEV back in 2013. It was Tim W. who made the NESRGB the commercial success it has become. If this wasn't for this work, a lot more PC10 systems would be killed for its RGB PPU.