The Sirius Joyport is a game controller adapter for the Apple II computer designed by Keithen Hayenga and Steve Woita (who were employed by Apple at the time) and then licensed for manufacture and distribution in 1981 by Sirius Software.[1]
The device was meant to address a limitation in the built-in game control offered by the Apple II, by allowing either four Apple-compatible paddles or two Atari CX40 joysticks (but not both types at once)[2] to be read by the computer simultaneously. The built-in game port on the Apple II, II+, IIe, and IIgs supports four analog paddles or two analog sticks, but only 3 buttons.
With the Joyport, a game can support twice as many players as with a standard Apple game port, but game designers had to specifically modify their code to take input from the Atari side of the Joyport.[3] Many of them did so, and this modification is what is often seen listed in Apple II game configuration screens as the "Atari Joyport" option.
The recommended Atari joysticks are switch-driven (i.e. digital), instead of the usual smoother-action analog sticks available for the Apple II.[3] Since the Apple II hardware makes no distinction between two paddles or a single analog joystick plugged into the same jack,[4] it is also been possible to connect and read two fully analog joysticks with the Joyport via the paddle jacks, but few (if any) two-joystick games supports this, and Sirius did not suggest it. Why not is unclear, but there may be a noticeable speed advantage when driving two digital rather than analog joysticks on the limited hardware of the time.[3]