Disk II
From Wikipedia, the free encyclopedia
The Disk II was a 5¼-inch floppy disk drive designed by Steve Wozniak and manufactured by Apple Computer. It was first introduced in 1978 at a retail price of US$495 for pre-order; it was later sold for $595 including the controller card and cable. The Disk II was designed specifically for use with the Apple II personal computer family to replace the slower cassette tape storage.
Contents |
[edit] History
The first drives sold were built using parts from Shugart Drives, but to reduce costs Apple switched to Alps Electric Co. of Japan who built them for half the cost. Early production at Apple was handled by two people, and they produced about thirty drives a day. [1] [2]
Normal storage capacity per disk side was 114KB with DOS 3.2.1 and earlier (13 256-byte sectors per track, 35 tracks per side), or 140KB with DOS 3.3 and the accompanying firmware update for the controller card (16 sectors/track). A Bell & Howell version of the Disk II was also manufactured by Apple in a black case which matched the color of the Bell & Howell version of the Apple II Plus which Apple was already manufacturing.
In 1978, Apple intended to develop its own FileWare drive mechanism for use in the new Apple /// and Lisa business computers being developed. They quickly ran into difficulties which precluded them from being incorporated in the Apple ///, which continued to use the earlier Shugart design.[3]
Apple later introduced the UniDisk 5.25", which modernized the appearance of the Disk II to better match the Apple IIe case, followed by a matching Platinum version they renamed Apple 5.25 Drive" (companion to the 800K Apple 3.5" Drive). All of these drives introduced a daisy chain pass-through port. They also offered a combination of two UniDisk drives in a single unit, called the DuoDisk, which could not be daisy chained, nor could a special Disk IIc, designed to match the Apple IIc.
In 1983 Apple announced the 860K FileWare drives as a replacement for the Disk II & III, but due to the notorious unreliability of the Apple-built so-called "Twiggy" drives in the Lisa, the products never shipped.[4][5]
[edit] Disk II Cable Pinout
This table shows the pinout of the original 1979 Disk II controller and newer 1983 Uni/Duo Disk I/O controller (655-0101).
The circuitry of these two controllers are identical. The Disk II header pin numbering is per the Disk II controller card silkscreen and the circuit schematic given in the DOS 3.3 manual. The Uni/Duo Disk D-19 pinout was derived from the controller card and comparison to the circuit schematic of the Disk II controller.
| Disk II Header Pin | Uni/Duo Disk D-19 Pin | Uni/Duo Controller Card Cable Color | Description |
|---|---|---|---|
| 1,3,5,7 | 1,2,3,4 | Brown,Orange,Green,Violet | Ground return |
| 2 | 11 | Red | Phase 0 stepper motor signal |
| 4 | 12 | Yellow | Phase 1 stepper motor signal |
| 6 | 13 | Blue | Phase 2 stepper motor signal |
| 8 | 14 | Grey | Phase 3 stepper motor signal |
| 9 | 5 | White | -12 volt power |
| 10 | 15 | Black | WR_REQ - write request signal |
| 11,12 | 6,16 | Brown,Red | +5 volt power |
| 13,15,17,19 | 7,8 | Orange,Green | +12 volt power |
| 14 | 17 | Yellow | ENABLE~ drive enable select signal |
| 16 | 18 | Blue | RD_DATA read data signal |
| 18 | 19 | Grey | WR_DATA write data signal |
| 20 | 10 | White | W_PROT write protect signal |
| x | 9 | Violet | No connect? |
- NOTE: Since most signals are shared with both drive 1 and drive 2, the logic in each drive uses the ENABLE~ signal to activate appropriately.
- Pin 14 for Disk II drive 1 and drive 2 have separate enable signals (14a and 14b)
- Pin 17 for Uni/Duo Disk is chained to first drive (drive 1) and second drive (drive 2) is enabled via other logic in the first drive. Perhaps the unused wire on pin 9 (no connect at the controller) is used for this purpose.
[edit] References
- ^ "A.P.P.L.E. Co-op Celebrates A Decade of Service", Call-A.P.P.L.E., Feb 1988: 12-27.
- ^ "Apple and Apple II History", The Apple II Guide, Cupertino, CA, Apple Computer, Inc., Fall 1990: 9-16.
- ^ Apple and the Floppy Drive
- ^ Apple's Twiggy Disks
- ^ Lisa2
[edit] See also
[edit] External links
- Apple II History - Chapter 5 (Disk II)
- Apple Floppy Disk II
- Apple Floppy Drives
- Disk II programming example
- Disk II Controller hardware article
- Apple II Diskette FAQ and Apple II Drive FAQ at comp.sys.apple2 FAQ mirror
