Pokey was a microprocessor in the Atari 8 bit range of computers (eg The Atari 800 XL and 130 XE). Its job was handling digital to analog and analog to digital conversion.
Sound
Pokey was most well known as the sound generator chip. It supported the following.
- 4 channels with a 2.5 octave range or 2 channels with an 8 octave range. You could also use 1 8 octave and 2 2.5 octave channels together.
- Sound distortion using either 9 or 17 bit poly counters to add randomness.
- Software volume control.
- A special effects channel. One "trick" I came across played a continuous low pitched note, and then cycled this channel from 0 to 255, resulting in a techno soundtrack!
Although there was no official playback of digitised sounds, some people hacked this in using the software volume control.
Tapes
Standard Atari tapes (on normal cassette tapes) were read and written at 600 baud using a standard FSK (Frequency Shift Keying) system. Both the A-D and D-A conversion was handled by Pokey.
The Atari 8-bit machines all used custom cassette recorders, which generally meant that tape loads were more reliable than those which used standard units. Some also drew their power from the host machine. Additionally, the computer signal was only recorded on one track, with the 2nd track being played through the TV's speakers. Some games used this as a way to play music during the load.
Paddles
Two paddle controllers could be connected into each joystick port. The A-D conversion was handled by Pokey.