Later on we had some "debug" cartridges that sat in between the console and a flash cartridge and intercepted reads/writes to a single address and replaced the data with whatever came in over a serial port back to the PC. That was enough of a backdoor to implement very basic dynamic reloading of art assets - I wrote a Photoshop plugin that added a "send to N64" button and some game-side support code and the cycle time for artists trying to see their work on a TV went from 30 minutes to 10 seconds.

Turns out it's actually a bit more complicated. The Partner-N64 uses some little-used analog input pins (LAUDIO, RAUDIO, VIDEO_SYNC) for this. The modification also requires cutting the lines to the system's DAC chip to work.

https://ultra64.ca/tutorials/make-your-own-partner-n64-conso...

This whole system feels so quirky and fiddly to work with compared to modern dev kits.

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Right. On Mobile Safari on first attempt to view the site

https://archive.is/WCnLA