Very high-density diskette format method and computer implemented process

#1. Field of the Invention

#The invention relates generally to magnetic disk drives and more specifically to diskette formats in very high track density drives and systems.

#2. Description of the Prior Art

#FIG. 1 is an elevational view of a prior art diskette in a hard plastic case and shows the media and hub that rotates within;

#FIGS. 2(a)-(b) illustrate the relationship of the media of FIG. 1 to the servo and nonservo side read/write heads and optical position detector. FIG. 2(a) is a elevational view of the optical servo side media and hub inside the diskette of FIG. 1. (Only one side has indelibly embossed, optically visible features.) FIG. 2(b) is a cross-sectional view of the media and heads taken along the line 2b-2b in FIG. 2(a);

#FIG. 3 is a top elevational view of a portion of the reference track. Both mechanically embossed and magnetically recorded features are illustrated;

#FIG. 1 illustrates a diskette of the present invention, referred to by the general reference numeral 10, which comprises a jacket 12, a label 14, a shutter 16, and a media 18. A liner (not shown) is disposed within jacket 12 and is made of a material that lubricates and cleans media 18. Media 18 is attached to a hub 20 and has a barium ferrite coating on both top and bottom surfaces (not shown for clarity in showing the other elements below). A hole 22 would normally be provided with a mechanical switch to indicate to a disk drive that diskette 10 is, or is not, write-protected, but in the present very high density (VHD) format, this hole is permanently set to indicate write protection in standard media drives. A hole 24 would normally indicate that diskette 10 is a high density (HD) format. The double density (DD) format is indicated by omitting hole 24. In diskette 10, hole 24 is preferably used as the write protect switch location.

#FIG. 2(a) illustrates, with circles drawn with dashed lines, that media 18 comprises indelibly embossed features that include a media type code (MTC) track 30, a reference track 32, and approximately 900 servo grooves 34 (numbered 0 to 899), all of which are concentric with one another. These indelibly embossed features consist of dashed lines having various patterns, depending on the track it is associated with. Servo grooves 34 are the simplest, with a 50% duty cycle pattern consisting of "stitches" that will generate a twenty kilohertz squarewave in an optical detector at the preferred media 18 rotational rate of 720 RPM. (Elements on the nonservo side that correspond to servo side elements are hereinafter numbered with prime notation; therefore reference track 32 on the servo side has a matching reference track 32' on the nonservo side in the same cylinder.) Interlaced into the spaces between the servo grooves 34, there are magnetically recorded a disk mapping table (DMT) track 36 and a plurality of magnetically recorded data tracks 38. A second DMT track 36' and plurality of data tracks are magnetically recorded on the nonservo surface at the same cylinder positions as those on the servo side. Presently, only one magnetically recorded track (36 or 38) is recorded between any two adjacent servo grooves 34. Certain minimum distances between magnetic data tracks must be maintained to avoid adjacent channel interference. The servo grooves 34 are used in a disk drive system to accurately position a pair of read/write head assemblies 50 comprising, on the nonservo side, a high density/double density (HD/DD) 5000 microinch gap magnetic core 51, a very high density (VHD) 600 microinch gap magnetic core 52, and on the servo side a VHD core 53, and a HD/DD core 54. The positioning system preferably has a conventional stepper motor that will position the assembly 50 to HD/DD track positions, and a finer voice coil positioning sub-system that rides on the stepper motor system and is activated for VHD use. The HD/DD cores 51 and 54 are used with the voice coil positioning sub-system in combination with the stepper motor system to read and write standard double density (800K) and high density (1.44M) diskettes. A reflective sensor system is used to provide a linear positioning scheme (not locked to the rotational surface) that compensates for offsets between the upper and lower heads, and that allows for trim-erasure before writing. Table One lists the physical track locations of the above from the center of media 18 in an exemplary embodiment. Table Two lists other preferred dimensions relating to the above grooves and tracks. There are 26 reference segments in the reference track and 1666 stitches in each servo track.

#TABLE ONE ______________________________________ MTC Track (cyl-6) 21.9390 mm Reference Track (cyl-3) 22.0000 mm Data Track 0 (cyl 0) 22.0610 mm Servo Groove 0 22.0510 mm Servo Groove 899 40.3906 mm ______________________________________