Browse Prior Art Database

Logical Sector Interleave

IP.com Disclosure Number: IPCOM000082199D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 4 page(s) / 103K

Publishing Venue

IBM

Related People

Guest, JE: AUTHOR [+3]

Abstract

The sectors forming a track in a disk storage drive are logically interleaved so as to improve sector density, and to optimize use of microprogram control and control elements.

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Logical Sector Interleave

The sectors forming a track in a disk storage drive are logically interleaved so as to improve sector density, and to optimize use of microprogram control and control elements.

The disk storage drive, not shown, includes magnetic disks for storing coded data in the form of magnetic bits. The magnetic disks are formatted so as to have a plurality of concentric tracks with a plurality of sectors within each track. In this instance, each track has sixty contiguous sectors physically numbered as shown by line C in Fig. 1. However, sector 30 is logically located adjacent to the right of sector 0 and sector 1 is similarly located adjacent to the right of sector 30, as seen in line D of Fig. 1. Correspondence between logical sector (LS) and physical sector (PS) locations is defined as:

(Image Omitted)

The format of a sector is illustrated at line E in Fig. 1. Note that the sector identification field (ID) precedes the data field. In order to write data into a data field, the sector is located by reading the sector ID and comparing it with the known or desired ID. If consecutive sectors are to be written, the logical sector interleave allows a full sector time for the combination read/write magnetic head to electrically recover, when switching from writing data field G to reading the next logical sector ID at J. This allows the gaps such as post data field gap G4 in line E1 to be a minimum, so as to increase the number of sectors per track.

The operation of the disk storage drive is controlled by microprogramming within a microprocessor, not shown. The microprogramming together with control circuitry in the disk storage drive attachment, not shown, initiate typical disk storage drive operations such as read, write or scan. The disk microcontrolled program (DMCP) is illustrated by the flow chart in Fig. 2. The disk file control unit (DFCU) is designed to operate on a single-sector basis initiated by the DMCP.

Data is transferred to and from storage a byte at a time using a cycle steal burst mode operation. The DMCP, illustrated by block 11, Fig. 2, interfaces with the disk input/output control system (DIOCS) 10. A start I/O read data command issued to DMCP from DIOCS initializes the disk control field address register (DCFAR) and the disk data field address register (DDFAR), block 12, if the disk storage drive is ready and not busy. This initiates hardware execution via a set start command,...