Coding a new BASIC interpreter in 2025 to replace a slow one

Summary

Developing a BASIC language interpreter in 2025 Recently, I had the chance to get an Intellivision II console along the ECS (Entertainment Computer System) and keyboard. I found and typed a game Bomb Run 1, using its integrated BASIC language, and I was pretty surprised to see how incredibly slow is it. Apparently, Mattel Electronics only developed the ECS to avoid paying a daily penalty of $10,000 dollars to the USA government because they were advertising a keyboard component that wasn't yet available. They developed the ECS in secret, while putting all their money in the ill-fated Keyboard Component which was a full 6502 computer around the Intellivision with an officially licensed MS-Basic. After getting the ECS on sale, Mattel forgot completely about it. It is a shame, because the keyboard is reasonable enough, it looks nice, and it could have been a nice starter BASIC platform. Anyway, the turtle speed intrigued me as I was pretty convinced that the Intellivision processor could do faster floating-point, so why not write my own extended BASIC interpreter? For the remaining of this article, the original Mattel ECS BASIC will be simply called ECS BASIC. System background The implementation of my extended BASIC interpreter is for a General Instruments CP1610 processor. This is a 16-bit processor introduced in 1975, with a resemblance to the PDP-11. However, General Instruments didn't allowed second sources, only wanted big orders, and ignored small requests (basically shooting itself in the foot), and this processor was used widely only in the Mattel Intellivision, and it ceased production in 1985 at the same time of the Intellivision demise. A full documentation of the instruction set is available along the jzintv emulator that can be downloaded from http://spatula-city.org/~im14u2c/intv/. I'll be using the basic 8K words between $5000-$6fff for the BASIC language, and I'll ignore altogether the EXEC (the Intellivision BIOS) and the ECS ROMs (I didn't even bothe...