The MOS Technology 8364 also known as Paula is a chip which includes logic for audio playback, floppy disk drive control and serial port input/output. It was used in all models of the Commodore Amiga, including the Commodore CDTV, the Amiga CD32, and Arcadia.
A 8364 contains the following elements:
- Digital to Analog converters.
- Disk control: a disk controller to read/write data from/to a floppy disk.
- UART control: a serial port controller to read/write data from/to a serial port.
- Pot control: four general purpose I/O ports with counters for Analog to Digital conversion which can be used for reading out analog joysticks.
- Interrupt control: handles internal and external interrupts
- DMA request logic: requests DMA cycles from the system DMA controller for the audio and disk controllers
Paula has four signed 8-bit DMA-driven audio channels. Each of the channels have independent frequency control and volume from 0 to 64.
By default, all channels loop. When a programmer wants a sample to play once, he either starts that sample and then immediately sets that channel's area to a mute sample (effective once the original sample ends), or stops the channel upon end (itself detected through one of aforementioned interrupts).
Finally, channels 1 and 4 are output analog through Paula's AUDL pin, and channels 2 and 3 through AUDR. This means that 2 channels are always hard left and 2 always hard right, which is a common complaint with headphones.
Some Amiga emulators and MOD players (as MOD originated from the Amiga) allow to reduce the stereo separation and do so by default.
- en.wikipedia.org/wiki/Paula_(computer_chip) - Wikipedia.