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The Integrated Woz Machine (or IWM for short) is a single-chip version of the floppy disk controller for the Apple II. It was also employed in Macintosh computers.
| | This article needs additional citations for verification .(December 2015) |
The Integrated Woz Machine (or IWM for short) is a single-chip version of the floppy disk controller for the Apple II. It was also employed in Macintosh computers.
When developing a floppy drive for the Apple II, Apple Inc. co-founder Steve Wozniak felt that the existing models available on the market were too complicated, expensive and inefficient. Rather than use the existing floppy drives from Shugart Associates, Wozniak decided to use the drive mechanism – but develop his own electronics separately for the both drive and the controller. [1] [2]
Wozniak successfully came up with a working floppy drive with a greatly reduced number of electronic components. Instead of storing 8–10 sectors (each holding 256 bytes of data) per track on a 5.25-inch floppy disk — something standard at that time, Wozniak utilized group-coded recording (GCR), and with 5-and-3 encoding he managed to squeeze as many as 13 sectors on each track using the same mechanics and the same storage medium. In a later revision, this number was bumped up to 16 sectors per track with 6-and-2 encoding. [1]
The floppy drive controller board, the "Disk II interface," [2] was built with 8 ICs, one of which is the PROM, containing tables for the encoder and decoder, the state machine, and some code.
To make it easier to move the controller onto the main board, as in the Apple IIc, Apple IIGS, and Macintosh, Dr. Wendell Sander integrated all these components into one single chip—the IWM. [3]
The IWM is essentially a disk controller on one IC. It was employed in the Apple IIc, and later Apple IIGS, the Apple Lisa 2/10, and all Mac models up to the Macintosh II. Later, an extended version, known as SWIM (Sander-Wozniak Integrated Machine), was introduced. This new version added the capability of reading and writing FM- and MFM-formatted (PC-formatted) floppy disks. In later Mac models, more and more peripheral components were added to the SWIM, until Apple finally phased out floppy drives from the Macs. The floppy controller function still stayed in the chipset for a while, even though the provision of floppy drives for the Macs had already ceased. For instance, the first iMacs still had a floppy drive connector on the motherboard, allowing a floppy drive to be retrofitted by knowledgeable enthusiasts. [4] [ self-published source? ]
The Apple II series is a family of home computers, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer, and launched in 1977 with the original Apple II.
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The Apple II is an early personal computer that was created by Apple Inc. It was one of the first successful mass-produced microcomputer products, and it played a significant role in the early development of the personal computer industry. It has an 8-bit microprocessor.
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The Macintosh SE is a personal computer designed, manufactured, and sold by Apple Computer, from March 1987 to October 1990. It marked a significant improvement on the Macintosh Plus design and was introduced by Apple at the same time as the Macintosh II.
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A floppy-disk controller (FDC) is a hardware component that directs and controls reading from and writing to a computer's floppy disk drive (FDD). It has evolved from a discrete set of components on one or more circuit boards to a special-purpose integrated circuit or a component thereof. An FDC is responsible for reading data presented from the host computer and converting it to the drive's on-disk format using one of a number of encoding schemes, like FM encoding or MFM encoding, and reading those formats and returning it to its original binary values.
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