This section only covers VSync Frequency: Original mode.
Although the UpserGrafx outputs a 720p signal, the signal isn't fully synchronized due to design constraints. As a result, a horizontal line may appear on the screen after using the UperGrafx continuously for a while. The signal can be fine tuned so that this line won't appear.
The UperGrafx and the PC Engine each have an internal crystal oscillator that need to be calibrated individually to improve timing accuracy. The timing can vary based on the crystal oscillator's individual characteristics and environment (primarily related to temperature).
This line represents the vsync synchronization border. If it moves too fast, it indicates that calibration is necessary. This line will also appear in 60.00Hz mode, but it will be moving around much too fast.
Once the yellow line shows little to no movement, the signal has been correctly calibrated.
The line will temporarily be placed in the center of the screen during calibration to make it easier to judge its movement.
Unfortunately, you will need to reset the video signal via one of the following two methods: