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Known Issue - GamePort functionality limitations

Batch #1 and #2 (thru Rev F) have some unintended limitations in functionality for the GamePort, particularly in MS-DOS.

Problem Description

The GamePort on the ITX-Llama interfaces with the Crystal CS4372B sound chip. During the design, it was observed that Crystal shares pins with other functions and a decision was made to limit joystick support to 2 axis, 2 buttons (Joystick #1) so that other features could be enabled. The pins used to communicate with the External FM Synth and S/PDIF audio output are also used for Buttons #3 and #4 of "Joystick #2". _As an unintended consequence, it was discovered that the Crystal chip mirrors/ghosts the signal data reserved for S/PDIF and the External FM module onto Buttons #3 and #4 despite "Joystick #2" being disabled.

Symptom

  • Joystick tests show excessive activity on buttons #3 and #4.
  • Games which use those buttons interact unexpectedly, skip cut scenes or behave erratically.
  • Calibration and button reassignment is not possible as the erratic activity skips or assigns buttons incorrectly.

Workaround

Disable the GamePort by forcing a mismatch in the port assignment.

  • In BIOS: Select Port 208h for the GamePort
  • In Autoexec.bat: Ensure SET BLASTER has J200 or J0 (if using the UNISOUND driver) at the end.

This mismatch will effectively disable the GamePort in DOS and prevent erratic button presses from causing games to misbehave.