Kempston Micro Electronics

Lore & Background

The Kempston Interface attached to the ZX Spectrum's rear expansion port and provided a single joystick port on the front or top of the system. Apart from implementing existing joystick interfacing modes, Kempston produced its own standard that delivered the joystick state on the Z80 bus at port 31, meaning the joystick did not produce key-presses like other standards such as Cursor. This method was soon borrowed by other interface manufacturers and became quite popular. The Kempston standard was one of the most widely supported standards on the machine, coming out as the clear winner against other standards such as Protek and AGF's cursor-based solution and the Fuller standard during the days of the 48K Spectrum.

Kempston Micro Electronics later became a distributor and reseller of the Competition Pro joystick in the United Kingdom, which led to the widespread misconception that Kempston had designed or manufactured the original Competition Pro models. The Competition Pro was originally developed by Coin Controls Ltd., with design work primarily attributed to Frank Happ of the company's U.S. operations, and Dutch company SUZO International also contributed to its development and manufacturing. The Competition Pro has a square base, two large red buttons, and a black pommel stick, using the Atari 2600 standard DE-9 connector.

Inserting or removing the joystick interface when the computer was turned on was inadvisable as it would almost certainly damage the computer hardware. When Amstrad released the ZX Spectrum +2, the computer featured a built-in joystick interface that was software-compatible with Sinclair's ZX Interface 2 standard, but the bundled SJS-1 joystick was electrically incompatible with the Atari standard.

Reader's Guide

The Kempston Interface established a de facto standard for joystick control on the ZX Spectrum, becoming one of the most widely supported standards on the machine. By delivering joystick state directly on the Z80 bus at port 31, it avoided the key-press simulation used by competing standards such as Cursor, Protek, AGF, and Fuller, and this method was soon adopted by other interface manufacturers. The interface's popularity meant that many games were written to support the Kempston standard, making it a key accessory for Spectrum owners.

The company's role as a distributor and reseller of the Competition Pro joystick in the UK further cemented its presence in the home computer market, though the widespread belief that Kempston designed or manufactured the original Competition Pro models is a misconception. The interface's use of the Atari joystick port standard (DE-9 connector) allowed compatibility with a wide range of controllers, and the Competition Pro joystick itself worked with the compatible ports of other home computers such as the Amstrad CPC, Commodore 64, VIC-20, and later Amiga and Atari ST. The Kempston Interface remains a notable example of how a third-party peripheral could define a platform's gaming experience.