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==Processor==
The central processor is a 65816, a backwards-compatible 16-bit update to the 6502 that was also used in the Super Nintendo. It runs natively at 2.8Mhz but will slow down to ~1Mhz when in classic Apple II emulation mode or when writing to video memory.
==Graphics Capabilities==
In addition to RGB emulations of the existing Apple II artefact composite video modes, the IIgs adds 320x200 and 640x200 RGB colour modes; the former in various combinations of 16 colours per line and the latter at 4 colours per line (including a hardware dithering mode that acts a little like 16 colours per line). Each line may use any of 16 palettes, making a total of 256 colours on screen without raster-linked palette changes.
There is also some support for 'fill mode', in which colour 0 means "repeat the last non-zero colour", designed to aid in fast single-colour fills.
Colours are selected from a 12-bit RGB 4,096 colour palette; the IIGS therefore has the same total colour range as its contemporaries the Commodore Amiga, the Atari STE and the Acorn Archimedes.
However it is subject to a number of deficiencies: there is a single buffer for video only — double buffering is not supported — and it supports neither hardware scrolling nor hardware sprites; and as all writes into video memory clock the CPU down to 1Mhz these are expensive to perform in software.
==Audio Capabilities==
The IIGS provides a 32-channel wavetable Ensoniq sound chip, which uses 64kb for samples.
The OS by default configures this as 15 stereo channels and uses the remaining two channels as interrupt counters; the IIGS is therefore often described as a 15-channel machine.
no edit summary
It was the first machine from Apple to use the Apple Desktop Bus and the first to provide a colour version of QuickDraw since the first colour Macintosh was not available until 1987. However it does not provide a high-resolution square pixel mode.
==Emulators==
{|class="wikitable" style="text-align:center"
!scope="col"|Name
!scope="col"|Operating systemPlatform(s)
!scope="col"|Latest version
!scope="col"|Active
!scope="col"|[[Recommended Emulators|Recommended]]
|-
! colspan="6"|PC / x86
|-
|[[KEGS]]
|Multi-platformalign=left|{{Icon|Windows|Linux|macOS}}|0.91{{KEGSVer}}
|{{✗}}
|{{✓}}
|-
|[[GSplus]]
|Multi-platformalign=left|{{Icon|Windows|Linux|macOS}}|0.14{{GSplusVer}}
|{{✓}}
|{{~}}
|-
|[[https://david-schmidt.github.io/gsport GSport]]|Multi-platformalign=left|{{Icon|Windows|Linux|macOS}}|0.31{{GSportVer}}|{{✗✓}}
|{{✗}}
|-
|[[MAME]]
|Multi-platformalign=left|{{Icon|Windows|Linux|macOS|FreeBSD}}
|{{MAMEVer}}
|{{✓}}
|{{✗}}
|}
==Processor==
The central processor is a 65816, a backwards-compatible 16-bit update to the 6502 that was also used in the Super Nintendo. It runs natively at 2.8Mhz but will slow down to ~1Mhz when in classic Apple II emulation mode or when writing to video memory.
==Graphics Capabilities==
In addition to RGB emulations of the existing Apple II artefact composite video modes, the IIgs adds 320x200 and 640x200 RGB colour modes; the former in various combinations of 16 colours per line and the latter at 4 colours per line (including a hardware dithering mode that acts a little like 16 colours per line). Each line may use any of 16 palettes, making a total of 256 colours on screen without raster-linked palette changes.
There is also some support for 'fill mode', in which colour 0 means "repeat the last non-zero colour", designed to aid in fast single-colour fills.
Colours are selected from a 12-bit RGB 4,096 colour palette; the IIGS therefore has the same total colour range as its contemporaries the Commodore Amiga, the Atari STE and the Acorn Archimedes.
However it is subject to a number of deficiencies: there is a single buffer for video only — double buffering is not supported — and it supports neither hardware scrolling nor hardware sprites; and as all writes into video memory clock the CPU down to 1Mhz these are expensive to perform in software.
==Audio Capabilities==
The IIGS provides a 32-channel wavetable Ensoniq sound chip, which uses 64kb for samples.
The OS by default configures this as 15 stereo channels and uses the remaining two channels as interrupt counters; the IIGS is therefore often described as a 15-channel machine.
{{Apple}}
