Integrated Woz Machine

The Integrated Woz Machine (IWM), codenamed "Liron", is a single-chip version of the floppy disk controller board used by Apple II series computers. It was also employed in early Macintosh computers.

History
When first developing a floppy drive for the Apple II, Apple Computer co-founder Steve Wozniak felt that the models available on the market were too complicated, expensive, and inefficient. Rather than use the existing floppy drives from, Wozniak decided to use only the drive mechanism, but develop his own electronics and controller for the drive.



Wozniak's design became the highly successful Disk II floppy drive and controller card, which contained a greatly reduced number of electronic components. Instead of storing 8–10 s (each holding 256 bytes of data) per on a 5.25-inch floppy disk (something standard at that time), Wozniak utilized  (GCR), and with  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. The Disk II floppy drive controller was originally built with 8 s (ICs), or microchips, two of which were the s (PROMs), containing tables for the encoder and decoder, the state machine, and some code.

Consolidation into the IWM
To make it easier to fit the drive controller into newer motherboard designs, Apple staff scientist Wendell Sander collaborated with Bob Bailey of to consolidate Wozniak's entire controller board onto a single chip that came to be known as the Integrated Woz Machine (IWM). Wendell Sander's involvement led to it sometimes being referred to as the "Integrated Wendell Machine". The IWM was employed in the Apple IIc, Apple II GS, and all early Macintosh models up to the Macintosh II. Later revisions of Apple II controller cards were also simplified by replacing pre-existing ICs with a single IWM chip.

Replacement by the SWIM
An updated version, known as the SWIM (Sander-Wozniak Integrated Machine), was introduced with the Macintosh IIx on September 19, 1988. This new version added the capability of reading and writing and -formatted (PC) floppy disks when paired with a FDHD mechanism, also marketed as "SuperDrive".

Discontinuation
The SWIM controller was used through most of the "beige" era of 68K and PowerPC Macs until it was phased out with the introduction of the iMac in 1998. The very first iMac G3 revision still had a SWIM and floppy drive connector on the motherboard, allowing a floppy drive to be retrofitted by knowledgeable enthusiasts.