Analog vs. Digital Gameport

Updated (08/12/14)
Written by Xevious

    Joysticks heavily evolved during the Gameport era, growing from simple two-axis, two-button game controllers to complicated devices with many buttons and using up to four axis.  DA15 joysticks are generally kept into two camps; Analog Joysticks, and Digital Joysticks. Knowing the differences of whether or not your DA15 joystick is Analog or Digital is the first step in determining if and how your joystick can be adapted for use with USB via adapters, or rewiring. 

Analog Joysticks

At it's inception in 1982, DA15 (or Gameport) was envisioned as a single port containing 15 pins.  Early joysticks were tailored to the simple games available at the time; most of these were 3rd person slide-scrolling programs and educational software.  Such joysticks as these, which adhere to the standards produced by IBM on the original PC in the early 80's and revised in the early 90's, are called Analog Joysticks.  Although IBM had intended the PC to have some entertainment and educational value, no one in the 1980's realized just what PC gaming would evolve into, or imagine the advent of newer gaming devices such as flight sticks, racing wheels, and gamepads.

IBM's Game Control Adapter released in the early 80's was a simple add-on card which was to be inserted into an ISA slot.  It would be the first DA15 controller, which originally supported two-axis and two buttons per controller.  At the time, it would be addressed and programmed directly by the applications which were run in the Disk Operating System (MS-DOS).  The operating system itself did not directly address the controller, and the card's address was fixed into the adapter.  In applications that did not need a joystick, it would not function.  In the early 1990's as the demands of Joysticks grew and newer devices such as Racing Wheels were introduced, the unused pins in DA15 were put into use in order to offer additional inputs and buttons.  Meanwhile audio cards such as the Sound Blaster began to include the DA15 adapter onboard it's own hardware, gradually eliminating the production of dedicated DA15 adapter cards.

Reference: DA15 Specification Sheet

At some point, Joystick manufacturers realized that you did not need to split the DA15 port to support two joysticks; you could instead dedicate a single DA15 port to use all of it's resources to the production of a joystick which would use all four axis and buttons.  This advance would herald the introduction of the first game pads (the concept would later be adapted by Nintendo for the famous NES) and the production of flight sticks which could use up three or four axis and four buttons such as the Gravis Blackhawk.  Yet, even these advances and changes in concept were not enough to satisfy gamers.  Computer gaming, particularly simulation gaming was becoming highly complicated.  Some joystick manufactures would include 13 or more buttons on their controllers by adding a PS/2 connector to the joystick which would route some of the extra joystick buttons to a programmable keyboard port, but the solution was ungainly. 

Early Digital Joysticks

Joystick manufacturers began to use signal mixing to produce joysticks which adhered to their own standards and did not strictly adhere to IBM's DA15 specification.  That is, instead of using a single pin on the DA15 port to address the joystick's functions, it would use a combination of pins per signal.  These controllers also posessed the first Point of View hats.  They would be the first Digital Joysticks.  These would require their own driver software in order to be utilized by Windows 95; in MS-DOS the game title would have to directly be programmed for it.  Even then, DA15 port was ultimately not able to handle the demands of newer and more complicated games and their correspondingly more intricate controllers. 

Later Digital Joysticks

As USB became more wide-spread with the release of Windows 95C, and later Windows 98, Joystick manufacturers began to produce joysticks which were designed for the USB interface.  They realized however, that the Gameport was not totally obsolete yet, and to satisfy that market niche they took joysticks designed for USB and modified them to function with the DA15 interface.  Such joysticks are designed fully for USB on the inside, but on the outside have the ability to send their fully digital signals through a game port.  Such joysticks were often shipped with adapters which allowed the controller to be used with USB OR Gameport, but some manufacturers would produce Gameport and USB versions of the same joystick, despite the face that internally their Gameport and USB versions were identical.  Once USB took hold of the market however, Gameport would be phased out after Windows XP.

    Any DA15 joystick which has up to 4 buttons, and 4 axis (including Rudder Pedals) is considered an Analog Joystick and most likely can be adapted using a Mayflash or a Rockfire USB to Gameport adapter in analog mode.  If your joystick has a POV hat and more than 4 buttons, it is most likely a Digital Joystick and needs either to use the special features on your USB to Gameport adapter, reprogramming, rewiring, or any combination of these things.  To put it more simply, early digital joysticks are the most difficult joysticks to adapt while analog joysticks enjoy loads of support that can carry them into the Windows 10 era. Later digital joysticks often also were released in both Gameport and USB versions, and the Gameport versions frequently had custom USB adapters made for them. Yet it is early digital joysticks which have the fondest memories for many players. How to adapt them for Windows 10 is the question.