Following the launch of the ZX Interface 2, a number of manufacturers produced equivalent interfaces providing joystick and ROM cartridge capabilities. Some of these interfaces extended the joystick functionality to also support the Kempston and Cursor standards. They were also more competitively priced than the ZX Interface 2.
The Kempston Pro interface supported the Kempston, Cursor and Sinclair standards, and retailed at £16.95.
There were two versions of the RAM Turbo produced. Both supported Kempston, Cursor and Sinclair joystick standards, had a full through edge connector and included a saftey guard to make if more difficult for the interface to be connected/disconnected whilst the power lead was plugged in. The latter version of the interface also included a reset button. By default the joystick sockets were configured to support the Sinclair standard, with one of the sockets simultaneously supporting the Kempston standard. The Cursor standard was selected by holding down the fire button whilst resetting the Spectrum. This approach was used since the method to read a Cursor joystick used the same IO ports as that for the Sinclair joysticks. After it became clear that ROM software was not a success the interface was subsequently sold without the ROM cartridge socket populated, thereby reducing manufacturing costs. The casing still retained the ROM cartridge socket opening and so it was possible to solder a socket onto the printed circuit board. The RAM Turbo interface retailed at £22.95, later dropping to £18.50.
The AGF RamSlot cost £9.95 and only provided ROM cartridge support.