Mocking board
The sound card Mockingboard (play on words with the English "mockingbird" - mocking thrush ) was an expansion card from Sweet Micro Systems for the Apple II or Apple IIc home computer and one of the world's first sound cards for private users. It was sold in different versions; the standard version offered six-part sound synthesis and could be upgraded to include a voice synthesis extension.
The Apple II only had very limited sound output options. His sound interface consisted of a built-in speaker whose membrane via software access back to a specific hardware address between two spatial positions and could be hergeschaltet - essentially equivalent to that of a more primitive version of the later IBM PC - System speaker . Using suitable programs, this output could be switched to the desired frequencies and thus emit tones. However, the Apple II had no programmable frequency generators , timers or interrupt sources , so the CPU had to take care of the entire sound generation - which made sound programs very complicated and practically prevented the execution of other tasks (such as changing the displayed screen content) while a sound was being output.
hardware
The mocking board was based on the AY-3-8910 sound chip , which had three independent square wave generators and a tunable noise generator . This chip was installed in many game consoles of the 1980s and later also in the Atari ST , so that a mocking board in the basic configuration delivered a comparable sound. The sound chip was controlled by the VIA 6522 interface chip , which also retrofitted the missing timer and interrupt sources on the Apple II. A 0.5 W output amplifier for connection to an 8 ohm loudspeaker completed the circuit.
Variants of the “mocking board” brought more than one sound chip and also offered the option of retrofitting the Votrax SC-01 speech synthesis chip. The largely compatible chip variant SC-223 was used later.