PC-DOS 1.2M format - Revision history

Jsummers: Category:MS-DOS

2017-03-29T16:30:26Z

Category:MS-DOS

Dan Tobias: /* Links */

2014-08-15T00:13:37Z

‎Links

Dan Tobias at 12:20, 24 February 2014

2014-02-24T12:20:17Z

Dan Tobias at 13:30, 23 August 2013

2013-08-23T13:30:41Z

Dan Tobias at 23:52, 9 May 2013

2013-05-09T23:52:30Z

Dan Tobias: Created page with "{{FormatInfo |formattype=physical |subcat=Floppy disk }} The '''PC-DOS 1.2M format''' (5 1/4", double sided, high density) was the high-density counterpart of the [[PC-DOS 36..."

2013-05-09T23:51:46Z

Created page with "{{FormatInfo |formattype=physical |subcat=Floppy disk }} The '''PC-DOS 1.2M format''' (5 1/4", double sided, high density) was the high-density counterpart of the [[PC-DOS 36..."

New page

{{FormatInfo
|formattype=physical
|subcat=Floppy disk
}}

The '''PC-DOS 1.2M format''' (5 1/4", double sided, high density) was the high-density counterpart of the [[PC-DOS 360K format]] for 5 1/4" [[floppy disk]]s, storing over 3 times as much data due to use of a different media surface capable of handling a higher density of data. It had 80 tracks per side, with 15 sectors per track, and 512 bytes per sector. Data was stored with [[MFM encoding]]. The disk turned at 360 RPM.

These disks were generally used with [[FAT12]] file systems under the MS-DOS or PC-DOS operating system. High-density disk drives could handle both the new 1.2 MB format and the old 360K format, though there were compatibility issues in reading 360K disks on low-density drives after they were written to with a high-density drive, even though the writing is done in an emulation of the old format, due to the different drive head on the newer drives. (The high-density drive heads were smaller, and the data written by them might not be picked up correctly by the larger low-density heads, particularly if the new data was overwriting data stored earlier using large-headed drives, which might not be completely overwritten.)

In the late '80s and early '90s, it was common for desktop PCs to have both 5 1/4" and 3 1/2" disk drives in order to be compatible with all software and data, which might be distributed on either format; by the 1990s these were usually high-density drives supporting the 1.2M [[PC-DOS 1.44M format|1.44M]] formats. Often the 5 1/4" drive was drive A, and the 3 1/2" one was drive B. Later PCs, however, were more likely to have only a 3 1/2" drive, set up to respond to both drive letters. Eventually, PCs stopped having floppy disk drives altogether as other data storage and transfer media took over.

[[Category:IBM]]
[[Category:Microsoft]]

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 == Links ==
 * [http://bitsavers.trailing-edge.com/pdf/panasonic/floppy/MSD891122000_JU-475-4_Service_Man.pdf Service manual for Panasonic JU-475-4 drive] (one disk drive model supporting this format)
 [[Category:IBM]]
 [[Category:Microsoft]]

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 These disks were generally used with [[FAT12]] file systems under the MS-DOS or PC-DOS operating system. High-density disk drives could handle both the new 1.2 MB format and the old 360K format, though there were compatibility issues in reading 360K disks on low-density drives after they were written to with a high-density drive, even though the writing is done in an emulation of the old format, due to the different drive head on the newer drives. (The high-density drive heads were smaller, and the data written by them might not be picked up correctly by the larger low-density heads, particularly if the new data was overwriting data stored earlier using large-headed drives, which might not be completely overwritten.)
-In the late '80s and early '90s, it was common for desktop PCs to have both 5 1/4" and 3 1/2" disk drives in order to be compatible with all software and data, which might be distributed on either format; by the 1990s these were usually high-density drives supporting the 1.2M [[PC-DOS 1.44M format|1.44M]] formats. Often the 5 1/4" drive was drive A, and the 3 1/2" one was drive B. Later PCs, however, were more likely to have only a 3 1/2" drive, set up to respond to both drive letters. Eventually, PCs stopped having floppy disk drives altogether as other data storage and transfer media took over.
+In the late '80s and early '90s, it was common for desktop PCs to have both 5 1/4" and 3 1/2" disk drives in order to be compatible with all software and data, which might be distributed on either format; by the 1990s these were usually high-density drives supporting the 1.2M and [[PC-DOS 1.44M format|1.44M]] formats. Often the 5 1/4" drive was drive A, and the 3 1/2" one was drive B. Later PCs, however, were more likely to have only a 3 1/2" drive, set up to respond to both drive letters. Eventually, PCs stopped having floppy disk drives altogether as other data storage and transfer media took over.
 [[Category:IBM]]
 [[Category:Microsoft]]

@@ Line 4: / Line 4: @@
 }}
-The '''PC-DOS 1.2M format''' (5 1/4", double sided, high density) was the high-density counterpart of the [[PC-DOS 360K format]] for 5 1/4" [[floppy disk]]s, storing over 3 times as much data due to use of a different media surface capable of handling a higher density of data. It had 80 tracks per side, with 15 sectors per track, and 512 bytes per sector. Data was stored with [[MFM encoding]]. The disk turned at 360 RPM.
+The '''PC-DOS 1.2M format''' (5 1/4", double sided, high density) was the high-density counterpart of the [[PC-DOS 360K format]] for 5 1/4" [[floppy disk]]s, storing over 3 times as much data due to use of a different media surface capable of handling a higher density of data. It had 80 tracks per side, with 15 sectors per track, and 512 bytes per sector. Data was stored with [[MFM encoding]]. The disk turned at 360 RPM. The high-density drives supporting this format were introduced in the mid-1980s with the IBM AT, and were commonplace by the end of the decade.
 These disks were generally used with [[FAT12]] file systems under the MS-DOS or PC-DOS operating system. High-density disk drives could handle both the new 1.2 MB format and the old 360K format, though there were compatibility issues in reading 360K disks on low-density drives after they were written to with a high-density drive, even though the writing is done in an emulation of the old format, due to the different drive head on the newer drives. (The high-density drive heads were smaller, and the data written by them might not be picked up correctly by the larger low-density heads, particularly if the new data was overwriting data stored earlier using large-headed drives, which might not be completely overwritten.)