Apple III Plus
 | |
| Apple III Plus | |
| Specifications | |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Type | Business Personal Computer |
| Released | December 1983 |
| Discontinued | April 1984 |
| Intro price | US$2,995 (1983) |
| CPU | Synertek 6502B @ 2 MHz |
| Memory | 256 KB RAM (expandable to 512 KB) |
| Storage | 5.25" floppy disk drive (built-in), external ProFile hard disk (optional) |
| Display | 24 lines × 80 columns text; 560×192 monochrome graphics |
| Sound | 1-bit beeper |
| Dimensions | 12" × 17" × 5" (30.5 × 43.2 × 12.7 cm) |
| Weight | 24 lb (10.9 kg) |
| OS / Firmware | Apple SOS, Apple III Business BASIC, Apple II emulation mode |
| Predecessor | Apple III |
| Codename | Mark Twain |
| Model no. | A3S2-1200, A3S2-1200A |
The Apple III Plus was the final revision of Apple’s business-oriented Apple III line, introduced in December 1983. It featured improved reliability, a built-in clock, and a standard 256 KB of RAM, but was discontinued just a few months later in April 1984.
Architecture and Processor
[edit | edit source]The Apple III Plus was powered by a Synertek 6502B microprocessor running at 2 MHz, offering double the clock speed of the original Apple II series. The system architecture was designed for business applications, with support for advanced operating systems and hardware expandability.
Key architectural features:
- 8-bit 6502B CPU @ 2 MHz
- Custom logic for memory management and peripheral support
- Apple II emulation mode via software for compatibility
Memory and Storage
[edit | edit source]The Apple III Plus shipped with:
- 256 KB RAM as standard, expandable to 512 KB via internal sockets
- Built-in 5.25" floppy disk drive (140 KB per disk, single-sided)
- Support for external ProFile hard disk drives (5 MB or 10 MB, optional)
- ROM containing Apple III firmware and Apple II emulation routines
The increased base RAM and improved memory management addressed many of the reliability issues of its predecessor.
Display and Graphics
[edit | edit source]The Apple III Plus supported:
- Text modes: 24 lines × 80 columns (business standard), 24×40 mode for Apple II compatibility
- Graphics modes: 560×192 pixels (monochrome), 280×192 (colour via Apple II emulation)
- Character generator ROM for text display
- Composite video output for monitors
These capabilities made the Apple III Plus suitable for business applications requiring high-resolution text and basic graphics.
Sound Capabilities
[edit | edit source]Sound on the Apple III Plus was limited to a simple 1-bit beeper, similar to the Apple II series. This was primarily used for system alerts and basic audio feedback.
Input/Output and Expansion
[edit | edit source]The Apple III Plus featured a range of I/O and expansion options:
- RS-232C serial port for printers and modems
- Parallel port (via optional card)
- Two Apple II–style internal expansion slots
- External floppy and hard disk interfaces
- Composite video output
- Keyboard and built-in numeric keypad
- Apple II emulation mode for running a wide range of Apple II software
These features allowed the Apple III Plus to serve both as a business workstation and as a bridge for users migrating from the Apple II.
Gallery
[edit | edit source]-
Front view of the Apple III Plus -
Rear panel with I/O ports -
Apple III Plus logic board open case
