Apple Disk II

Apple Computer, Inc. sold the Disk II floppy disk subsystem for $495 with controller and DOS, enabling the Apple II to access 113 kilobytes per diskette and up to nearly 1.6 megabytes with multiple drives.

The Disk II Disk Drive, officially the Apple Disk II Floppy Disk Subsystem, was a 5¼" floppy drive peripheral designed to work with the Apple II series⁴. It shipped in two primary configurations: model A2M0044 (with controller card), later revised as A2M0044E for compatibility with the Apple II and IIe, and model A2M0003 without the controller card³7. An adapter kit, part number A2M2006, allowed older drives to interface with the Apple IIe³.

Apple positioned the Disk II as a complete storage solution comprising an intelligent interface card, DOS 3.3, and one or two drives⁴¹⁵. The system used a ROM-based bootstrap loader and loaded its operating system into RAM, allowing full disk functionality even on systems with only 16K of memory⁴. Despite this flexibility, the Disk II and its controller imposed hardware limitations on software development, a constraint noted in contemporary technical literature¹⁰.

Storage capacity was rated at 113 kilobytes per diskette⁴. Access time was advertised as under half a second for any record⁴. The Apple II could support up to fourteen Disk II drives via seven interface cards without requiring an expansion chassis, theoretically aggregating nearly 1.6 megabytes of storage⁴.

Compatibility extended across the Apple II line: the Apple II, Apple II Plus¹², Apple IIe (with adapter)³, and Apple IIGS⁹. Third-party hardware such as Micro-Sci A2 drives and controllers were direct plug-in replacements⁶. Software support included DOS 3.3 from Apple Computer Co.¹⁰ and utilities like Gus's Disk Utility, which operated under DOS 3.1 or 3.2⁵. Apple II Pascal v. 1.3 required either two 5.25-inch drives or one 3.5-inch drive with 64K RAM, indicating the Disk II’s role in enabling more advanced development workflows⁹.

The Disk II was marketed as part of Apple’s line of “smart peripherals” that required no chassis expansion; users simply plugged them into available slots and powered on⁴. It was listed alongside the Parallel Printer Interface (A2B0002X) and Communication Interface (A2B0003X), with future peripherals like the Printer II and Modem IIA teased in promotional materials⁴. The universal DOS command processor allowed integration with existing languages and monitors, broadening its utility beyond basic file storage⁴.

Despite its widespread adoption, the surviving documentation is silent on physical dimensions, power requirements, internal microprocessor details, and production volume. The 1978 source referencing the $495 price point confirms availability by that year, but no exact release or discontinuation dates are present in the record⁴. The Disk II’s design, soft-sectored and supporting random or sequential access and program chaining, reflected a pragmatic balance of cost and functionality that made disk storage accessible to early personal computer users, even if its technical ceiling was quickly outpaced⁴.

Specifications

References

1. 1980 05 BYTE 05-05 Floppy Disks (1980)
2. Apple Parts Lists 1984 (1984)
3. Apple II Cable and Connector Guide
4. 1978 07 BYTE 03-07 How To Get Your Tarbell Going (1978)
5. MICRO Vol26-7 80
6. 1983 03 BYTE 08-03 Mass Storage (1983)
7. Apple II Cable and Connector Guide
8. BYTE Vol 07-05 1982-05 Japanese Computers (1982)
9. APDAlog 199104 (1991)
10. MICRO Vol61-06 83
11. 1982 12 BYTE 07-12 Game Plan 1982 (1982)
12. Interface Age-1981-06 (1981)
13. a2 const1 user
14. 1980 09 BYTE 05-09 Homebrewing (1980)
15. A2F0084 AppleAtAGlance 0582
16. 1984 02 BYTE 09-02 Benchmarks (1984)