Apple IIGS

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The Apple IIGS was the last model of the Apple II series of personal computers made by Apple Computer. At the time of its release it had stunning color video and sound capabilities that surpassed those of the Macintosh; although the black and white Macs had a slight edge in vertical resolution. The "GS" in its name, in fact, stood for "Graphics" and "Sound." The IIGS supported numerous new hardware and software features as well as full compatibility with earlier Apple II models, but Apple paid it relatively little attention as the company increasingly focused on the Macintosh platform.

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Appleiigs_computer.jpg
An Apple IIGS with an external floppy drive and mouse
Contents

Background

The IIGS was released in September 1986. It competed with personal computers such as the Commodore Amiga and Atari ST at the time of its release and was also popular with schools, but Apple failed to promote and update the IIGS, preferring to focus on the Macintosh instead. This lack of attention caused the IIGS to fall increasingly far behind other personal computers over its lifetime, and Apple ceased production of it in December 1992.

Hardware features

The Apple IIGS was an innovative computer with many improvements over the older Apple IIe and Apple IIc. It used the new Western Design Center 65816 16-bit microprocessor running at 2.8 MHz, which was faster than the 8-bit 6502 and 65C02 processors used in earlier Apple IIs and also allowed the IIGS to use more RAM. It also included enhanced graphics and sound, which led to its name. The graphics of the IIGS were the best of the Apple II series, with new Super High Resolution (SHR) video modes. These included a 640×200-pixel mode with 2-bit palletized color and a 320×200-pixel mode with 4-bit palletized color, both of which could dip into to a 4,096 color palette. By changing the palette on each scanline, it was possible to display up to 256 colors or more per screen, which was quite commonly seen within game and graphic design software. Audio was generated by a built-in sound and music synthesizer in the form of the Ensoniq Digital Oscillator Chip (DOC), which had it's own dedicated RAM and 32 separate channels of sound, which were paired to produce 15 voices, in stereo audio.

The IIGS could support both 5¼-inch and 3½-inch floppy disks and, like the IIe before it, had several expansion slots. These included seven general-purpose expansion slots compatible with those on the Apple II, II+, and IIe, plus a memory expansion slot that could be used to add up to 8MB of RAM. The IIGS, like the IIc, also had dedicated ports for external devices. These included a port to attach floppy disk drives, two serial ports for devices such as printers and modems (which could also be used to connect to a LocalTalk network), an Apple Desktop Bus port to connect the keyboard and mouse, and composite and RGB video ports.

Hardware revisions

Although Apple never introduced a substantially enhanced version of the IIGS after its initial release, it did create several slightly revised hardware versions.

  • The initial version, often known as the "ROM 0," was the one introduced in September 1986.
  • In September 1987, a slightly revised version known as the "ROM 01" was introduced. This included updated ROM routines, and ROM 0 machines could be updated to ROM 01 by replacing the computer's ROM chip with an updated one. (Some ROM 0 machines also included faulty Video Graphics Controller chips which were replaced when performing the ROM 01 upgrade.) Authorized Apple dealers could perform the upgrade from ROM 0 to ROM 01. ROM 01 is the minimum version needed to run later versions of the Apple IIGS System Software based on GS/OS rather than ProDOS 16.
  • The final released hardware revision was known as the "ROM 3," which came out in August 1989. The ROM 3 IIGS included a revised motherboard, so it was not possible to upgrade earlier machines to it by replacing chips. It included more updates to the software included in the ROM, as well as an improved motherboard design featuring 1 MB of built-in RAM rather than 256 KB (although all revisions could be upgraded to a total of 8 MB). The motherboard design was also designed to increase audio quality and allow more power to be delivered to cards in the expansion slots.
  • Some work was done on a "ROM 4" design featuring more features integrated onto the motherboard and into the case, but it was never released (although a few individuals outside of Apple did obtain prototypes). This model, called variously the Apple IIGS+, the ROM 4, or "Mark Twain" (after his famous misquote regarding the exaggeration of his death), had an internal floppy and SCSI hard drive, and an included 2 30 pin SIMM sockets for memory expansion. It ran at the standard 2.8 mhz of preceding IIGS hardware versions.

Hardware versions from ROM 01 onward display the ROM version on the bottom of the screen when starting up.

Graphics modes

In addition to supporting all graphics modes of previous Apple II models, the Apple IIGS introduced several new ones through a custom Video Graphics Chip (VGC), all of which used a 12-bit palette for a total of 4096 possible colors.

  • 320×200 pixels with a single palette of 16 colors.
  • 320×200 pixels with up to 16 palettes of 16 colors. In this mode, the VGC holds 16 separate palettes of 16 colors in its own memory. Each of the 200 scan lines can be assigned any one of these palettes allowing for up to 256 colors on the screen at once. This mode is handled entirely by the VGC with no CPU assistance, making it perfect for games and high-speed animation.
  • 320×200 pixels with up to 200 palettes of 16 colors. In this mode, the CPU assists the VGC in swapping palettes in and out of the video memory so that each scan line can have its own palette of 16 colors allowing for up to 3200 colors on the screen at once. This mode is computationally-intensive however, and is only suitable for viewing graphics or in paint programs.
  • 640×200 pixels with four pure colors. This mode is generally only used for ensuring that the Apple logo and menu bar retain their colors in Desktop applications.
  • 640×200 pixels with 16 dithered colors. In this mode, two palettes of four pure colors each are used in alternating columns. The hardware then dithers the colors of adjacent pixels to create 16 total colors on the screen. This mode is generally used for programs requiring finer detail such as word processors and the Finder.

Additionally, through the use of scan line interrupts, graphics modes could be mixed on the screen. This is most often seen in graphics programs where the menu bar is constantly in 640-pixel resolution and the working area's mode can be changed depending on the user's needs.

Later on, video cards such as Sequential Systems' Second Sight added SVGA modes allowing 24-bit color to the Apple IIGS.

Audio features

The Apple IIGS' sound was provided by an included Ensoniq 5503 DOC wavetable sound chip, the same chip used in Ensoniq's Mirage and ESQ-1 professional-grade synthesizers. The chip allowed for 32 separate channels of sound, though most software paired them into 16 stereo voices, as did the standard tools of the operating system. The IIGS is often referred to as a fifteen-voice system, though, since one stereo voice is reserved by the OS at all times for timing and system sounds. Software that doesn't use the OS, or uses custom-programmed tools (most games and demos do this), can access the chip directly and take advantage of all 32 voices.

A headphone jack (providing monaural sound) was provided on the back of the case, and standard stereo computer speakers could be attached there. A third party adapter card was however required to produce true two-channel stereo, despite the fact the Ensoniq and virtually all native software produced stereo audio.

Expansion capabilities

The IIGS was highly expandable. The expansion slots could be used for a variety of purposes, greatly increasing the computer's capabilities. SCSI host adaptors could be used to connect external SCSI devices such as hard drives and CD-ROM drives. Other mass storage devices such as adaptors supporting internal 2.5-inch IDE hard drives could also be used. Another common class of expansion cards was accelerator cards replacing the computer's original processor with a faster one. A variety of other cards were also produced, including ones allowing new technologies such as 10BASE-T Ethernet and CompactFlash cards to be used on the IIGS.

Development and codenames

Apple's first internal project to develop a next-generation Apple II based on the 65816 was known as the "IIx." The IIx project, though, became bogged down when it attempted to include various coprocessors allowing it to emulate other computer systems. Early samples on the 65816 were also problematic. These problems led to the cancellation of the IIx project, but somewhat later a new project was formed to produce an updated Apple II. This project, which led to the released IIGS, was known by various codenames while the new system was being developed, including "Phoenix," "Rambo," "Gumby," and "Cortland."

Influence on later computers

The Apple Desktop Bus, which for a long time was the standard for most input peripherals for the Macintosh, first appeared on the Apple IIGS.

Though including a professional-grade sound chip in the Apple IIGS was hailed by developers and users both, and hopes were high that it would be added to the Macintosh, it drew a lawsuit by Apple Records. As part of an earlier trademark dispute with the record company, Apple Computer had agreed not to release music-related products. Apple Records considered the inclusion of the Ensoniq chip in the IIGS as a violation of that agreement. Though the IIGS was allowed to keep the Ensoniq, Apple has not included dedicated hardware sound synthesizers in any of its Macintosh models (though of course, third-party products exist).

Software features

Broadly speaking, software that runs on the Apple IIGS can be divided into two major categories: 8-bit software compatible with earlier Apple II systems such as the IIe and IIc, and 16-bit IIGS-specific software, most of which runs under the Apple IIGS System Software and takes advantage of its advanced features, including a Macintosh-like graphical user interface.

8-bit Apple II compatibility

The Apple IIGS was almost completely backward compatible with older Apple II computers, so users wouldn't be left with large libraries of useless software. The IIGS could run all of Apple's earlier Apple II operating systems: Apple DOS, ProDOS 8, and Apple Pascal. It was also compatible with nearly all 8-bit software running under those systems. Like the Apple II+, IIe, and IIc, the IIGS also included Applesoft BASIC and a monitor (which could be used for very simple assembly language programming) in ROM, so they could be used even with no operating system loaded from disk.

Apple IIGS System Software

The Apple IIGS System Software utilized a Graphical user interface (GUI) very similar to the Apple Macintosh's and somewhat like GEM for PCs and the operating systems of contemporary Atari and Amiga computers. Initial versions of the System Software were based on the ProDOS 16 operating system, which was based on the original ProDOS operating system for 8-bit Apple II computers. Although it was modified so that 16-bit Apple IIGS software could run on it, ProDOS 16 was written largely in 8-bit code and did not take full advantage of the IIGS's capabilities. Later System Software versions (starting with version 4.0) replaced ProDOS 16 with a new 16-bit operating system known as GS/OS. It better utilized the unique capabilities of the IIGS and included many valuable new features. The Apple IIGS System Software was substantially enhanced and expanded over the years during which it was developed, culminating in its final version, System 6.0.1, which was released in 1993.

Graphical user interface

The IIGS System Software provided a mouse-driven graphical user interface using concepts such as windows, menus, and icons. This was implemented by a '"toolbox" of code, some of which resided in the computer's ROM and some of which was loaded from disk. The IIGS GUI was very similar to that of early Macintoshes. One major application could run at a time, although other smaller programs known as Desk Accessories could be used simultaneously. The IIGS had a Finder application very similar to the Macintosh's, which allowed the user to manipulate files and launch applications. By default, the Finder was displayed when the computer started up and whenever the user quit an application that had been started from it, although the startup application could be changed by the user.

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The IIGS Finder allows easy exploration of disks' contents. New Desk Accessories such as the Calculator can be run at the same time as applications such as the Finder.

Extensibility

The IIGS System Software could be extended through various mechanisms. New Desk Accessories were small programs ranging from a calculator to simple word processors that could be used while running any standard desktop application. Classic Desk Accessories also served as small programs available while running other applications, but they used the text screen and could be accessed even from non-desktop applications. Control Panels and initialization files were other mechanisms that allowed various functions to be added to the system. Finder Extras permitted new capabilities to be added to the Finder, drivers could be used to support new hardware devices, and users could also add "tools" that provided various functions that other programs could utilize easily. These features could be used to provide features never planned for by the system's designers, such as a TCP/IP stack known as "Marinetti."

Multitasking Capability

An interesting feature of the IIGS was that multitasking was possible. A UNIX-like multitasking kernel was produced, called GNO/ME, which ran under the GUI and provided preemptive multitasking. In addition, a system called The Manager could be used to make the Finder more like the one on the Macintosh, allowing major software (other than just the "accessory" programs) to run simultaneously through cooperative multitasking.

See also

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