Apple double-density 3 1/2" disk
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The '''Apple double-density 3 1/2" disk''' was used on the Macintosh (with the [[MFS]] or [[HFS]] file system) and the Apple II line (with the [[ProDOS file system]]). It was a disk format with 80 tracks per side and a variable 8 to 12 sectors per track, with each sector storing 512 bytes. When used in single-sided mode, its capacity was 400 kilobytes; this became 800 in double-sided mode. Data was encoded using a form of [[GCR encoding]]. The drive ran at constant linear velocity (CLV), meaning that the RPM rate varied depending on which track was being read. | The '''Apple double-density 3 1/2" disk''' was used on the Macintosh (with the [[MFS]] or [[HFS]] file system) and the Apple II line (with the [[ProDOS file system]]). It was a disk format with 80 tracks per side and a variable 8 to 12 sectors per track, with each sector storing 512 bytes. When used in single-sided mode, its capacity was 400 kilobytes; this became 800 in double-sided mode. Data was encoded using a form of [[GCR encoding]]. The drive ran at constant linear velocity (CLV), meaning that the RPM rate varied depending on which track was being read. | ||
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| + | The [[Apple high-density 3 1/2" disk]] is the high-density counterpart of this format, on higher-capacity physical media introduced later. | ||
3 1/2" disks are actually 90 mm wide, but are almost universally referred to as "3 1/2 inch" disks even in countries that use the metric system. | 3 1/2" disks are actually 90 mm wide, but are almost universally referred to as "3 1/2 inch" disks even in countries that use the metric system. | ||
Revision as of 12:35, 14 November 2014
The Apple double-density 3 1/2" disk was used on the Macintosh (with the MFS or HFS file system) and the Apple II line (with the ProDOS file system). It was a disk format with 80 tracks per side and a variable 8 to 12 sectors per track, with each sector storing 512 bytes. When used in single-sided mode, its capacity was 400 kilobytes; this became 800 in double-sided mode. Data was encoded using a form of GCR encoding. The drive ran at constant linear velocity (CLV), meaning that the RPM rate varied depending on which track was being read.
The Apple high-density 3 1/2" disk is the high-density counterpart of this format, on higher-capacity physical media introduced later.
3 1/2" disks are actually 90 mm wide, but are almost universally referred to as "3 1/2 inch" disks even in countries that use the metric system.
