Spectrum owners who thought they were getting their hands on a Microdrive for a mere £49.95 were dismayed to discover that you couldn't simply plug the device into the computer, but required an additional interface. The Interface I was released at the same time as the Microdrive and, as long as you bought the pair as a set, cost an extra £29.95 (or £49.95 as a separate item). Unlike the precarious RAM packs for the ZX81, the design of the new interface was professional and stable. It simply plugged into the back of the Spectrum and was secured by a couple of screws to the computer's underside. Apart from controlling the Microdrives, the Interface I facilitated two other functions. The device offered 'standard' RS232 facilities, which allowed Spectrum users access to a wide range of printers and modems. It also offered a simple 'local area network' option, which essentially means that up to 64 Spectrums can be connected together, communicate at relatively high speeds and share Microdrives and printers. The Interface I was praised by users and reviewers alike, and was generally considered to be a well-designed and efficient addition to the Spectrum's hardware.

The ugly sister of the Spectrum peripherals was released in September 1983 with little in the way of fanfare and to about as much interest. The Interface II was designed to allow users of the machine to use joysticks and ROM software cartridges. The device disappeared without a trace within twelve months. The reason for such a riot of indifference was that independent peripherals producers had been selling joystick interfaces almost since the day the Spectrum was released, and that the Interface II allowed the use only of digital 'switchtype' (rather than potentiometer, or analogue) joysticks. Owners rightly decided that the ROM cartridges simply weren't likely to be produced by a sufficient number of software houses to make the device worth their investment. Furthermore, at a cost of £19.95 the cartridges offered software at three or four times the price of a tape. So why bother? And very few did.