The 3-inch compact floppy disk

10:17 AM 0 Comments


Throughout the early 1980s the limitations of the 5¼-inch format were starting to become clear. Originally designed to be smaller and more practical than the 8-inch format, the 5¼-inch system was itself too large, and as the quality of the recording media grew, the same amount of data could be placed on a smaller surface. Another problem was that the 5¼-inch disks were simply scaled down versions of the 8-inch disks, which had never really been engineered for ease of use. The thin folded-plastic shell allowed the disk to be easily damaged through bending, and allowed dirt to get onto the disk surface through the opening.

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The "Twiggy" disk


In the early '80s, Apple fell victim to a serious case of NIH Syndrome (Not Invented Here), and decided to manufacture their own disk drives. Not content to be industry compatible, instead they designed what they believed to be leading-edge drives: the Twiggy floppy drive and the Widget hard drive.
The Twiggy floppy drive was a double-sided drive, but unlike conventional double-sided drives the heads were not directly opposing. Instead the heads were on opposite sides of the spindle, and opposing each head was a pressure pad (as commonly used in single-sided drives). This was supposed to reduce head wear. It also meant that the stiff jackets of the floppy media had to have non-standard cutouts. The write-protect cutout was moved to the side of the disk that would be nearest the back of the drive. One corner of the disk was notched for "keying" to prevent the user from inserting the disk incorrectly. A rectangular hole near that corner was apparently for use to latch the disk in the drive, preventing the user from removing it while it was in an inconsistent state. 

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The 5¼-inch mini floppy

10:09 AM 0 Comments


In a 1976 meeting, An Wang of Wang Laboratories informed Shugart Associates' Jim Adkinson and Don Massaro, that the 8-inch format was simply too large for the desktop word processing machines he was developing at the time. Adkinson and Massaro proposed a 5¼-inches wide format which Wang accepted. Shugart Associates then developed a new drive of this size storing 98.5 KB later increased to 110 KB by adding 5 tracks. The 5¼-inch drive was considerably less expensive than 8-inch drives from IBM, and soon started appearing on CP/M machines. At one point Shugart was producing 4,000 drives a day. By 1978 there were more than 10 manufacturers producing 5¼-inch floppy drives, in competing physical disk formats: hard-sectored (90 KB) and soft-sectored (110 KB). The 5¼-inch formats quickly displaced the 8-inch for most applications, and the 5¼-inch hard-sectored disk format eventually disappeared.
Apple introduced the 5¼-inch Disk II for the Apple II in 1978, using GCR encoding to store 35 tracks of 13 sectors of 256 bytes (113KB). An upgrade to a more sophisticated GCR scheme in 1980 increased track capacity to 16 sectors (140KB for the disk).
These early drives read only one side of the disk, leading to the popular budget approach of cutting a second write-enable slot and index hole into the carrier envelope and flipping it over (thus, the “flippy disk”) to use the other side for additional storage. This was considered risky by some, for the reason that single sided disks would only be certified by the manufacturer for single sided use. In reality, since some single-head floppy drives had their read/write heads on the bottom and some had them on the top, disk manufacturers routinely certified both sides of disks for use, thus the method was perfectly safe. An alternate reasoning was that when flipped the disk would spin in the opposite direction inside its cover, so some of the dirt that had been collected by the fabric lining in the previous rotations would be picked up by the disk and dragged past the read/write head.
Tandon introduced a double-sided drive in 1978, doubling the capacity, and a new “double density” format increased it again, to 360 KB

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