Browse Prior Art Database

Simplification of Hard Disk Read and Write Commands Code

IP.com Disclosure Number: IPCOM000103986D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 1 page(s) / 31K

Publishing Venue

IBM

Related People

Gonzalez, JP: AUTHOR

Abstract

This article describes a technique for use in a computer system using Read-Multiple and Write-Multiple controller commands even for single sector reads or writes rather than select Read Single and Write Single commands. The original read and write commands only transfer one sector of data per interrupt. The newer Read-Multiple and Write-Multiple commands are intended to break this limitation. By using these commands, multiple sectors can now be transferred with only one interrupt. But now the software has two sets of commands that are very similar. Instead of developing and supporting code for both sets of commands, one set of commands can be used to cover the functionality of the other.

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Simplification of Hard Disk Read and Write Commands Code

           This article describes a technique for use in a computer
system using Read-Multiple and Write-Multiple controller commands
even for single sector reads or writes rather than select Read Single
and Write Single commands.
     The original read and write commands only transfer one sector of
data per interrupt.  The newer Read-Multiple and Write-Multiple
commands are intended to break this limitation.  By using these
commands, multiple sectors can now be transferred with only one
interrupt.  But now the software has two sets of commands that are
very similar.  Instead of developing and supporting code for both
sets of commands, one set of commands can be used to cover the
functionality of the other.
     Even though the Read-Multiple and Write-Multiple commands were
intended for transfers involving multiple sectors, their use can be
extended to cover the instances of reading/writing a single sector.
This can be achieved by simply changing the sector count register of
the disk drive to indicate a 1 before executing the command.
     The advantage of doing this is that now, the basic read/write
command is redundant and can be completely eliminated.  Using
read/write-multiples for all reads and writes saves lines of code and
processing delays associated with keeping track of the two different
types of commands.

Disclosed Anonymously.