Sinclair Research ZX Interface 2 peripheral

The joystick ports actually map Sinclair joystick controls to keyboard presses. Other joysticks will not work in the ports. Having 2 joystick ports was most popular feature of the ZXi2.

Due to technical limitations, ZXi2 cartridges cannot include RAM. The design of the ZXi2 and ZX Spectrum units are hostile to bankswitching. Despite this, programmers have designed cartridges of 64k, 128k, 256k, and 512k in size. These cartridges are not without unusual limits. 512k cartridges, for example, can only load 8k at a time (half the speed of a standard cartridge). Plus, they have an unusually high software overhead required to load data from this half speed interface and they will be loading the different 8k segments a lot. Still, it is faster than loading from a cassette or disk, which is the main reason to use cartridges on 8-bit computers.