Apple IIGS

Apple IIGS

Apple IIGS (ROM 01, 1986)
Specifications
Manufacturer	Apple Computer, Inc.
Type	Personal Computer
Released	September 15, 1986
Discontinued	December 1992
Intro price	US$999 (base, 1986)
CPU	Western Design Center 65C816 @ 2.8 MHz
Memory	256 KB RAM (expandable to 8 MB)
Storage	3.5" 800 KB and 5.25" 140 KB floppy drives, optional SCSI hard disk
Display	320×200 or 640×200 pixels, 4,096 colours (up to 256 on screen)
Sound	Ensoniq 5503 Digital Oscillator Chip (32-channel, stereo)
Dimensions	38.1 cm × 36.8 cm × 8.3 cm
Weight	4.1 kg
OS / Firmware	GS/OS, ProDOS 16, ProDOS 8
Predecessor	Apple IIe
Codename	Cortland
Model no.	A2S6000 (original), A2S6001 (ROM 01), A2S6003 (ROM 03)

The Apple IIGS is a 16-bit personal computer introduced by Apple Computer, Inc. in September 1986 as the most advanced and final model in the Apple II series. It combined backward compatibility with earlier Apple II software and hardware with enhanced graphics and sound, targeting both education and home users.

Architecture and Processor

The IIGS was built around the Western Design Center 65C816 microprocessor, a 16-bit extension of the classic 6502 architecture. Key features include:

• CPU: WDC 65C816 running at 2.8 MHz (software-switchable to 1 MHz for compatibility)
• 16-bit data bus and 24-bit address bus, supporting up to 8 MB of RAM
• Backward compatibility with 8-bit Apple II software via a hardware emulation mode

The 65C816 enabled the IIGS to run new, more powerful applications while maintaining support for the extensive Apple II software library.

Memory and Storage

The standard Apple IIGS shipped with 256 KB RAM, expandable via memory expansion cards to a maximum of 8 MB. ROM versions evolved over time:

• ROM 00/01: 128 KB ROM
• ROM 03: 256 KB ROM, improved firmware and self-test

Storage options included:

• 3.5" 800 KB floppy drive (Apple 3.5 Drive)
• 5.25" 140 KB floppy drive (Apple Disk II or DuoDisk)
• Optional SCSI hard disk (via expansion card)
• Support for ProDOS and GS/OS file systems

Display and Graphics

The IIGS introduced advanced graphics capabilities for the Apple II line, powered by custom VGC (Video Graphics Controller) hardware:

• Resolution: 320×200 (up to 256 colours), 640×200 (up to 16 colours)
• Palette: 4,096 colours (12-bit RGB), with programmable palettes per scanline
• Hardware support for text and graphics modes, including double high-resolution and super high-resolution
• Backward compatibility with all previous Apple II video modes

These features enabled the IIGS to display rich, colourful graphics far beyond earlier Apple II models.

Sound Capabilities

A major innovation was the inclusion of the Ensoniq 5503 Digital Oscillator Chip (DOC), a professional-grade synthesiser chip:

• 32 independent digital oscillators
• Stereo output (two 8-bit DACs)
• Programmable waveforms, envelopes, and mixing
• Backward-compatible with Apple II speaker output

The Ensoniq DOC gave the IIGS sound capabilities comparable to contemporary synthesiser keyboards and workstations, making it a favourite for music and educational software.

Input/Output and Expansion

The IIGS retained the Apple II’s renowned expandability:

• Seven Apple II-style internal slots for cards (including SCSI, memory, networking, and accelerators)
• Dedicated memory expansion slot
• Ports:
  • ADB (Apple Desktop Bus) for keyboard and mouse (first Apple II to use ADB)
  • Printer (serial), modem (serial), and joystick ports
  • Composite video, RGB video, and mono audio out
• External drive connectors for 3.5" and 5.25" floppy drives

This flexibility allowed the IIGS to serve in classrooms, homes, and professional environments.

Gallery

• 
  Apple IIGS (front view)
• 
  Apple IIGS Logic Board & Power Supply
• 
  Apple IIGS with peripherals