Williams Hardware Identification and Compatibility
Stargate, Robotron, Joust, Splat! and Sinistar CPU Boards

The games Stargate, Robotron, Joust, Splat! and Sinistar all share common CPU boards with 4 different revisions. This page allows you to identify them, view a high resolution image for comparison with your own boards and download the schematics pertaining to the particular board revision. Defender and Bubbles CPU boards are not covered here, for them see the main Williams Hardware compatibility page

R8948 (Revision -) CPU Board Shipped with Stargate games only Identifiable by small daughterboard at the bottom of the board and 5770-09656-00 etched above battery holder Links for this PCB: High Resolution Image (123kB) Schematics (not online) Note: The Stargate CPU BS.BA Inversion modification must be carried out on all R8948 (Revision -) boards in order to use it with later games (Robotron, Joust, Splat! and Sinistar).	R8731 (Revision B) CPU Board Shipped with Stargate and Robotron games Identifiable by two wire BS.BA inversion factory modification and 5770-09656-00 Rev. B etched above battery holder Links for this PCB: High Resolution Image (119kB) Schematics (not online) Note: This CPU is capable of running Stargate, Robotron, Joust, Splat! and Sinistar without modification.
R8731 (Revision C) CPU Board Shipped with Robotron, Joust and Sinistar games? Identifiable by 5770-09656-00 Rev. C etched above battery holder Links for this PCB: High Resolution Image (103kB) Schematics (not online) Note: This CPU is capable of running Stargate, Robotron, Joust, Splat! and Sinistar without modification.	R8731 (Revision D) CPU Board Shipped with Robotron, Joust and Sinistar games? Identifiable by inductors next to the PCB power connector and 5770-09656-00 Rev. D etched above battery holder Links for this PCB: High Resolution Image (120kB) Schematics (1.3MB) Note: This CPU is capable of running Stargate, Robotron, Joust, Splat! and Sinistar without modification.

Notes:

1. The Stargate CPU BS.BA Inversion modification must be carried out on all R8948 (no revision) boards in order to use it with later games (Robotron, Joust, Splat! and Sinistar). If this is not done no damage will occur, however the boards will appear DEAD!
   
   
2. Boards shipped with Stargate games had Decoder ROMs 4+5 fitted, however, all later games had Decoder ROMs 4+6 fitted. It may be the case that your PCB has different combinations of decoder ROMs due to incorrect replacement. Decoder ROMs work in the following combinations; 1+3, 2+3, 4+5 and 4+6. However RAM diagnostics may give incorrect information when using 1+3 and 2+3. Additionally, Decoder 1 will not work with cocktail games.
   
   
3. Do not confuse the CPU boards for Stargate, Robotron, Joust, Splat! and Sinistar with Defender and Bubbles as although they look similar they will not work, it will appear as if the game were dead. Defender and Bubbles CPU boards are covered on the main Williams Hardware compatibility page.