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 at the end.

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