Apple IIGS(1986)

歴史的背景

A radical departure from the existing Apple II line, the IIGS featured a true 16-bit microprocessor, the 65C816, operating at 2.8 MHz with 24-bit addressing, allowing expansion up to 8 MB of RAM without the bank-switching hassles of the earlier machines. It introduced two completely new graphic modes sporting higher resolutions and a palette of 4,096 colors; however, only 4 (at 640×200 resolution) or 16 (at 320×200 resolution) colors could be used on a single line at a time. The Apple IIGS stood out from any previous (or future) Apple II models, evolving and advancing the platform into the next generation of computing while still maintaining near-complete backward compatibility. The secret of the Apple IIGS's compatibility was a single chip called the Mega II, which contained the functional equivalent of an entire Apple IIe computer (sans processor). This, combined with the flawless 65C02 emulation mode of the 65C816 processor, provided full support for legacy software. The computer also included a 32-voice Ensoniq 5503, 'wavetable' sample-based music synthesizer chip with 64 KB dedicated RAM, 256 KB of standard RAM, built-in peripheral ports (switchable between IIe-style card slots and IIc-style onboard controllers for disk drives, mouse, RGB video, and serial devices), built-in AppleTalk networking, and a ROM toolbox that supported a graphical user interface derived from the Macintosh toolbox. The computer could run existing 8-bit Apple II software (including software written for the very first Apple II in Integer BASIC), but also supported 16-bit software running under a new OS first called ProDOS 16 and later called GS/OS. The new OS eventually included a Finder that could be used for managing disks and files and opening documents and applications, along with desk accessories – just like the Macintosh. The 16-bit operating system would automatically switch to the text display and downshift to 8-bit mode to run legacy software, while offering a consistent, Macintosh-like graphical interface for native 16-bit applications. Eventually, the IIGS gained the ability to read and write Macintosh disks and, through third-party software, even multitasking (both cooperative and preemptive, the latter in the form of a Unix-type shell), outline TrueType font support, and in one case, even real-time 3D gaming using texture mapping. The first 50,000 Apple IIGS computers came with Steve Wozniak's "Woz" signature silkscreened on the front and were referred to as the "Woz Limited Edition".