I was wondering how he managed to do this. He actually wrote an emulator running on the 4004 with memory hacks for more ROM space that simulates a DEC MIPS R3000 processor, a disk device that accesses a SD card, and a UART that prints on a 2x40 display. Absolute genius level!

Any normal 32bit operation on the MIPS is a hard job for the poor 4004, which works with 4 bits per operation and sometimes needs to do some carry flag magic, too. The MIPS thinks it runs at 1MHz, but actually it runs at 74Hz, so a second in it’s world takes 4 hours in reality.

This is an impressive feat! Hats off and a deep bow to Dmitry Grinberg for this project!