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Browse Prior Art Database

Relative Block Addressing in an Advanced Technology Integrated Device Electronics File Subsystem

IP.com Disclosure Number: IPCOM000105940D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 4 page(s) / 112K

Publishing Venue

IBM

Related People

Furness, JP: AUTHOR [+2]

Abstract

This article describes a means for relative block addressing (RBA) that fits within the existing structure of an advanced technology (AT) file interface.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Relative Block Addressing in an Advanced Technology Integrated Device Electronics File Subsystem

       Fig. 1

      This article describes a means for relative block addressing
(RBA) that fits within the existing structure of an advanced
technology (AT) file interface.

      The most common method of attaching a high performance direct
access storage device (DASD) to personal computers is via an AT
interface which includes AT-IDE (Integrated Device Electronics), and
ATA (AT Attachment).

      Presently, fixed disks employing the ATA are accessed by
providing an address which directly relates the file geometry.  This
severely restricts DASD manufacturers in the format they may use for
storage, and imposes a difficult accounting system for the operating
system.

      A means is provided herein for RBA fits within the existing
structure of the AT file interface.

      The ATA is based upon a device level interface.  In a true
device level interface, the controlling circuitry is located on a
separate adapter card, physically distinct from the drive.
Formatting, head selection, error detection, etc. is all done on the
adapter itself, not on the drive.  All the drive does is the actual
mechanical operation of positioning heads and reading and writing.

      Because the adapter has to issue very low level instructions to
the drive, the address generated by the host has to adhere to the way
the drive is designed.  Since most fixed disk drives have multiple
cylinders consisting of a fixed number of tracks composed of a fixed
number of sectors, this is the addressing methodology that is
employed and is the file structure used by PC operating systems.
Primarily, for reasons of software compatibility, this "cylinder,
head and sector" (CHS) address is the method adopted by the ATA.

      The CHS address map is a three dimensional structure.  This is
a difficult and time consuming technique of maintaining information.
(Matrix manipulation is well understood, but requires a lot of
mathematical processing.)

      Fig. 1 depicts the logical progression of address in a typical
CHS address map.  (For a device with four heads.)

      Further, DASD manufacturers would like to employ various design
techniques to increase capacity or improve yield.

Among these are:

o   Zone recording, in which varying the number of sectors per track
    takes advantage of the fact that the recording areas are not
    constant throughout the diameter of a platter.

o   Transparent defect management, in which the device may reassign a
    defect unbeknownst to...