411 REFERENCE · Wikibooks
X86 Assembly/Programmable Parallel Interface
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
The Original x86 PC had another peripheral chip onboard known as the 8255A Programmable Peripheral Interface (PPI). The 8255A, and variants (82C55A, 82B55A, etc.) controlled the communications tasks with the outside world. The PPI chips can be programmed to operate in different I/O modes.