Other graphics boards require many USR() statements to execute machine-code routines.
This board patches the ROM to change the BASIC language, which makes it very easy to use.
I've added 32K static RAM to my board, to reduce the number of wobbly connections and allow the use of a single 5V power supply.

This amazing upgrade belies the enormous amount of cleverness packing the functionality into a handful of TTL chips and a tiny 2K EPROM. It has been integrated into a ZX81 emulator if you want to try it out!