Pre-Game ASIC Operation (Game Gear)

Once you have red light boot, the next step is confirm your ASIC is running as expected out of reset with no game.

The ASIC regardless of game or not, right after reset should start clocking out a valid VSYNC and HSYNC signal, as well as the alternative DW (VSync) and CL2 (HSync) signals. we will use the DW and CL2 signals here.

DW VSYNC (pin 20 on LCD ribbon, pin 51 of IC3 on 2-ASIC, pin 50 on 1-ASIC). should look like this (a 16.7ms pulse width signal indicating the start of each frame of the image).

CL2 HSYNC (pin 9 on LCD ribbon, pin 46 of IC3 on 2-ASIC, pin 55 on 1-ASIC) should look like this (a 63.8us pulse width signal indicating the start of each line of a single frame of the image).

This confirms the ASIC is operational. After this the ASIC should attempt to read the game file from the cartridge and with the assistance of the main RAM start running the game code.

During initial boot the ASIC sends out specific signals to the game cartridge that help identify successful running operation. Below are the signals you can probe to determine the next steps of boot are happening.

The CClock (pin 40 of the cartridge connector, pin 5 of 2-ASIC, pin 31 of 1-ASIC) has a clock of around 3.579Mhz. Although most games do not even connect to this pin, it is useful to see correct ASIC operation.