The first Display Adapter was installed in the model 5570-S, also known as the first Micro Channel machine of PS/55. It had a compatibility problem with PS/2 applications. Since the model 5550-S released in 1988, the Display Adapter II that improved the PS/2 compatibility was introduced. In the boot sequence, the Display Adapter enables VGA on the motherboard, and it passes the video signal from the motherboard to adapter's VGA connector. When using Japanese DOS, VGA is disabled, and the Display Adapter switches its video selector from VGA to own video chip. In addition, it added the 256 color mode (1024×768 pixels in 256 colors chosen from 262,144 colors). The adapter has 1 MB of video RAM, and 256 KB of RAM for user-defined characters.
