What may possibly be the weirdest Famicom mod idea ever (HDMI processor)

[maxellnormalbias]

I was having a discussion on Discord that was originally joking - "oh, i'm gonna make an adapter to hook up a Switch to a Famicom. Like a Wide Boy, but for the Switch."

And then I realized it was possible.

It would involve implementing a high-resolution video out on the Famicom, which has been done before by Kevtris et al. More interestingly, it's been done by Famiclone manufacturers such as Hamy for quite a while now. They use a commercial video processor IC to tap directly into the RGB lines of a globtop Famicom-on-a-chip and program the firmware to scale it. Video processor ICs can do much more than scale RGB data, though - they can overlay it on top of existing video, etc.

This is an ASCII drawing of how this would work in the internals of the Famicom. A video processor chip would handle PPU scaling. When HDMI needs to be passed through, an internal PRG ROM will idle the CPU indefinitely while the CPU lines on the cartridge are repurposed as a backplane for HDMI signals (TMDS lanes). PPU memory can still be puppeted by the cartridge in the manner of the Wide Boy to produce interesting overlays that could serve as a secondary method of display for e.g. a configuration menu.

It seems self-explanatory as to how something like a Switch dock could be implemented. Just have a RAM-adaptor-esque cartridge carries HDMI from an existing Switch dock, maybe fashioned to look vaguely like a Disk System.

However, this opens up a lot of possibilities:

• A video player cartridge that stores movies (or gets them from the internet) and uses an H.264 decoder IC in combination with PPU manipulation for a video selection menu.


• A raspberry pi cartridge that can be used as a media centre or similar.


• Other consoles minimized to the size of Famicom cartridges.

There's a few downsides, mainly the fact that it allows the famicom to be puppeted by a chipset in the cartridge, leaving one to wonder why you need the famicom anyways. I still think it would be neat to see the famicom revived as a backplane for more advanced devices. The great thing about the Famicom/NES is that it's universal - no matter where you lived, there was some official or cloned version of the system available. It's a shared platform of enjoyment that spans countries and generations. It would be a bit poetic to see a standard derived from the famicom to become "universal" again.

EDIT: Attached the ascii art drawing since the pastebin seems to have been taken down.