Apple II Plus
 | |
| Apple II Plus – Enhanced Apple II Series Model | |
| Specifications | |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Type | Home Computer |
| Released | June 1979 |
| Discontinued | December 1982 |
| Intro price | US$1,195 (1979) |
| CPU | MOS Technology 6502 @ 1.023 MHz |
| Memory | 48 KB RAM (expandable to 64 KB), 12 KB ROM (Integer BASIC, Applesoft BASIC, Monitor) |
| Storage | External cassette tape, optional 5.25" floppy disk drive (Disk II) |
| Display | 40×24 text, 280×192 graphics (6 colours), 16-colour low-res mode |
| Sound | 1-bit built-in speaker (toggle via software) |
| Dimensions | 38.1 cm × 45.7 cm × 10.2 cm |
| Weight | 5.9 kg |
| OS / Firmware | Apple DOS 3.2, 3.3; ProDOS (later) |
| Predecessor | Apple II |
| Successor | Apple IIe |
| Model no. | A2S1048, A2S1049 |
The Apple II Plus is the second model in Apple Computer’s influential Apple II series, introduced in June 1979. It featured expanded memory, the introduction of Applesoft BASIC in ROM, and compatibility with a growing ecosystem of expansion cards, making it a mainstay of home, educational, and business computing into the early 1980s.
Architecture and Processor
[edit | edit source]At its core, the Apple II Plus is powered by the MOS Technology 6502 microprocessor, running at 1.023 MHz. The 6502 was an 8-bit CPU widely adopted in early personal computers for its simplicity and low cost. The Apple II Plus architecture is fully compatible with the original Apple II, but adds improved firmware and ROM routines.
Key architectural features:
- 8-bit data bus, 16-bit address bus (64 KB addressable space)
- Integer BASIC in ROM replaced by Applesoft BASIC (floating-point support)
- Built-in system monitor in ROM for low-level programming and diagnostics
Memory and Storage
[edit | edit source]The standard Apple II Plus shipped with 48 KB RAM, expandable to 64 KB via an additional 16 KB language card in slot 0. ROM was expanded to 12 KB, containing:
- Applesoft BASIC (8 KB)
- Monitor ROM (2 KB)
- Autostart ROM (2 KB, for improved booting and disk support)
Storage options included:
- Cassette tape interface (standard, for program and data storage)
- Optional Disk II 5.25" floppy drive (introduced in 1978, widely adopted by II Plus users)
- Third-party and later Apple expansion cards enabled hard disk, RAM disk, and other storage forms
Display and Graphics
[edit | edit source]The Apple II Plus used the same video subsystem as the original Apple II, providing:
- Text modes: 40 columns × 24 rows (upper/lowercase with third-party mods)
- Low-resolution graphics: 40×48 pixels, 16 colours
- High-resolution graphics: 280×192 pixels, 6 colours (colour availability depends on NTSC artifacting)
- Composite video output for direct connection to colour or monochrome monitors and televisions
The graphics system was memory-mapped, allowing direct manipulation of the display by software.
Sound Capabilities
[edit | edit source]Sound on the Apple II Plus was simple but effective for its era:
- 1-bit built-in speaker, toggled by writing to a memory-mapped address ($C030)
- Programmable by software for single-channel beeps, clicks, and simple tones
- More advanced sound (multi-voice, music, speech) was possible with third-party sound cards and peripherals
Input/Output and Expansion
[edit | edit source]The Apple II Plus was renowned for its expandability, featuring eight internal expansion slots for peripherals such as:
- Disk II controller cards (for floppy drives)
- Language cards (RAM expansion)
- Serial and parallel interface cards (printers, modems)
- Video and graphics enhancements
- Sound and speech synthesiser cards
- Networking and hard disk controllers
Standard I/O ports included:
- Composite video output
- Cassette in/out
- Game I/O connector (paddle/joystick support)
- Keyboard (built-in)
- Expansion slots (8)
PCB Schematics & Service Manual
[edit | edit source]The Apple II Plus main logic board is a single-sided PCB integrating the CPU, RAM, ROM, video, and bus logic. Several revisions exist, with minor changes to support additional RAM or improved reliability.
| Logic Board | Schematic Diagrams |
|---|---|
 |
The official Apple II Plus Reference Manual and Apple II Plus Technical Reference Manual provide comprehensive schematics, troubleshooting, and service procedures.
Gallery
[edit | edit source]-
Apple II Plus front view -
Apple II Plus with Disk Drives -
Apple II Plus motherboard
