Disk II

歴史的背景

The Disk II Floppy Disk Subsystem is a 5.25-inch floppy disk drive designed by Steve Wozniak at the recommendation of Mike Markkula. Apple did not originally offer a disk drive for the Apple II, which used data cassette storage like other microcomputers of the time. It was announced in June 1978 at a retail price of $495 U.S. for pre-order; it was later sold for $595 U.S. including the controller card (which can control up to two drives) and cable. The initial Disk II drives (A2M0003) were modifications of the Shugart SA-400, which was the first commercially available 5.25-inch diskette drive. Apple purchased only the bare drive mechanisms without the standard SA-400 controller board, replaced it with Wozniak's disk interface board design, and then stamped the Apple logo onto the faceplate. Wozniak called the resultant Disk II system "my most incredible experience at Apple and the finest job I did", and credited it and VisiCalc with the Apple II's success. Early production at Apple was handled by two people, and they assembled 30 drives a day. By 1982, Apple switched to Alps drives for cost reasons. The drive connected to the controller card via a 20-pin ribbon cable; the controller card was plugged into one of the bus slots on the Apple II's logicboard. DB-19 adapters were eventually available for use with Apple's later connector standard. Up to 14 drives could be attached to one Apple II or Apple IIe computer - two drives per controller card, one card per slot, and there were seven usable slots per computer. Apple's printed manuals suggested using slot 6 for the first controller card.