RGB / S-Video upgrade for Nintendo NES

I developed a board that can be installed inside a NES or Famicom to improve the video quality. This is not a replacement PPU (Picture Processing Unit, the NES graphics chip) nor does require any parts from Nintendo arcade hardware. The original idea came from HardWareMan and thefox on the NesDev forum.

The NESRGB board effectively bypasses parts of the PPU - Palette RAM (Color Generator), Decoder, and DAC. These functions are duplicated in the NESRGB board with a focus on video quality. The timing of the video is unchanged so there is no lag (no framebuffer, no VGA, no HDMI, etc, etc), just non-interlaced 15kHz video output.







I have uploaded some high res screen shot photos here:

http://etim.net.au/nesrgb/announcement/photos/



Drakon has created video captures from the board (Youtube links).

Gimmick, Castlevania 3, Kirby's Adventure

Full Castlevania 3 Playthrough





How it works (technical)



Refer to the operation block diagram. The PPU part of the diagram is taken from US patent number 4824106.



An Altera PLD sits between the PPU and the CPU data bus. When the CPU writes data into the Palette Ram (Color Generator) the data is captured and stored in the NESRGB board. Modified data is passed to the PPU. The PLD also intercepts writes to the register controlling the operation of the Multiplexer, making EXT0-3 outputs. The modified data passed to the PPU removes data already available at the EXT0-3 outputs. The rest of the information required (EXT4, blanking, and sync) is extracted from the video output with comparators. The video data is then decoded from the palette currently selected and passed out to the DAC and video encoder.



Features

User selectable palette. Three palettes available, I call them Natural, Improved, and Garish. The Natural palette has the same colours as the normal composite video output. It comes from the Nestopia NES emulator. Improved is from the FCEUX emulator. There is more variety in the colours. Some games look significantly better with this one. Garish is also from the Nintendulator but it is a palette from the Nintendo Playchoice PPU. It's very colourful indeed. More of a curiosity than anything else. There is a fourth choice - if no palette is selected the NESRGB board will 'turn off' and just pass data through. This way the NES will output composite video as if the board was not installed at all.

Built in audio and video amplifier. Useful for the Famicom which does not have A/V outputs already.

Outputs RGB, S-video (encoded from RGB), composite video (encoded from RGB), and composite video (original from PPU).

Compatible with PAL and NTSC consoles (jumper selectable).

Supplied with audio/video connectors, three position switch, and other assorted bits that may be required for installation.

Size in mm 98.2 * 52.5 * 3.7



Installation



The NESRGB board is designed with the NES front loader in mind. It sits in a socket where the PPU normally lives. The PPU is mounted in the NESRGB board. See the picture below as an example (ignore the jumble of wires soldered to the card edge finger at the bottom of the NES motherboard, it is not related to the installation). It also shows a separate voltage regulator board which is recommended for the original NES because the its own voltage regulator heat sink is small and may get too hot with the additional load from the NESRGB board.

The board may also be installed into AV Famicom and top loading NES models when a suitable pin adapter board is fitted.

Guide for

Switch wiring info - A three position toggle switch is now included instead of a slide switch.

Software and Errata

Where to buy



Buy from etim online shop (Australia, International),



Updated installer/distributor page.



For questions and comments please email.

