1.) Pulse Wave
The DMG-CPU B was the primary CPU of the Game Boy. It had a built in audio processing unit (APU) which included a PSG which was designed by Satoru Okada and Hirokazu Tanaka. This PSG was US patent publication number US5095798 A, it was filed on 1990-01-08, published on 1992-03-17, and given application number 07/462,491.
The PSG consists of four channels, two pulse waves, a programmable wave, and a noise channel. Volume envelopes are supported on both square waves and the noise channel. The first square wave supports a frequency sweep, and the programmable wave supports up to 32 4-bit samples. The noise channel supports a frequency range from 2-1,048,576 Hz, and the other three channels support a frequency range of 64-131,072 Hz.
The DMG-CPU B on a Game Boy circuit board.
Most Game Boy emulators and GBS players can emulate the audio functions of the DMG-CPU B.
- google.com/patents/US5095798 - US patent information.