Editing CHIP-8 (section)

==CHIP-8 extensions and variations==

During the 1970s and 1980s, CHIP-8 users shared CHIP-8 programs, but also changes and extensions to the CHIP-8 interpreter, like in the VIPER magazine for COSMAC VIP. These extensions included CHIP-10 and Hi-Res CHIP-8, which introduced a higher resolution than the standard 64x32, and CHIP-8C and CHIP-8X, which extended the monochrome display capabilities to support limited color, among other features. {{refn|[https://github.com/mattmikolay/chip-8/wiki/CHIP%E2%80%908-Extensions-Reference CHIP‐8 Extensions Reference] by Matthew Mikolay}} These extensions were mostly backwards compatible, as they were based on the original interpreter, although some repurposed rarely used opcodes for new instructions. {{refn|https://github.com/trapexit/chip-8_documentation}}

In 1979, [[Electronics Australia]] ran a series of articles on building a kit computer similar to the COSMAC VIP, based on the [[Motorola 6800]] architecture. {{refn|https://archive.org/stream/EA1979/EA%201979-05%20May#page/n85/mode/2up}} This computer, the DREAM 6800, came with its own version of CHIP-8. A newsletter similar to VIPER, called DREAMER{{refn|https://archive.org/details/dreamer_newsletter_01/mode/2up}}, was used to share CHIP-8 games for this interpreter. In 1981, [[Electronics Today International]] (ETI) ran a series of articles on building a computer, the ETI-660, which was also very similar to the VIP (and used the same microprocessor). ETI ran regular ETI-660 and general CHIP-8 columns{{refn|https://archive.org/stream/ETIA1981/ETI%201981-11%20November#page/n113/mode/2up}} until 1985.

In 1990, a CHIP-8 interpreter called CHIP-48 was made by Andreas Gustafsson <ref>{{cite web | url=https://github.com/Chromatophore/HP48-Superchip/blob/master/binaries/source/c48_source.txt | title=CHIP-48 source code | website=[[GitHub]] }}</ref> for [[HP-48]] [[graphing calculator]]s. Erik Bryntse later created another interpreter based on CHIP-48,<ref>[http://devernay.free.fr/hacks/chip8/schip.txt SCHIP 1.1 documentation]</ref> titled "SUPER-CHIP",  often shortened to SCHIP or S-CHIP. SCHIP extended the CHIP-8 language with a larger resolution and several additional opcodes meant to make programming easier. {{refn|[https://github.com/Chromatophore/HP48-Superchip HP48-Superchip] Repository on [[GitHub]]}}

David Winter's interpreter, disassembler, and extended technical documentation popularized CHIP-8/SCHIP on other platforms. It laid out a complete list of undocumented opcodes and features{{refn|[https://web.archive.org/web/20140825173007/http://vanbeveren.byethost13.com/stuff/CHIP8.pdf CHIP8.pdf] by David WINTER (HPMANIAC)}} and was distributed across hobbyist forums. Many interpreters used these works as a starting point.{{Citation needed|date=May 2024|reason=What interpreters?}}

However, CHIP-48 subtly changed the semantics of a few of the opcodes, and SCHIP continued to use those new semantics in addition to changing other opcodes. Many online resources about CHIP-8 propagate these new semantics, so many modern CHIP-8 games are not [[Backward compatibility|backwards compatible]] with the original CHIP-8 interpreter for the COSMAC VIP, even if they do not specifically use the new SCHIP extensions. {{refn|name=compatibility|[https://github.com/JohnEarnest/Octo/blob/gh-pages/docs/SuperChip.md#compatibility Mastering SuperChip] Compatibility section}}

Some extensions take opcodes or behavior from multiple extensions, like XO-CHIP which takes some from behavior from SCHIP and CHIP-8E. <ref>{{cite web | url=https://github.com/JohnEarnest/Octo/blob/gh-pages/docs/XO-ChipSpecification.md | title=XO-CHIP Specification by John Earnest | website=[[GitHub]] }}</ref>