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June 23, 2010 T13/2132-D Revision 3
Working Draft Enhanced Disk Drive - 4 (EDD-4) xi
Foreword
Foreword
(This foreword is not part of American National Standard NCITS.xxx-200x)
DOS accesses its mass storage devices using an INT13h programming interface provided by BIOS firmware to
higher-level software. This interface was designed in the early 1980's, upgraded in the late 1980's and upgraded
again in the early 1990's. Initially, INT 13h used a cylinder-head-sector interface that was limited to approx.
528MB of disk addressing. Later this same interface was upgraded to support approx. 8.4GB of disk
addressing. Finally, extended functions were created that allowed 64-bit disk addressing. At this same time,
specifications were created that allowed the CD or DVD ROM drive to boot using the same INT 13h interface that
hard drives used. The Disk and CD/DVD functions have never been fully documented in a standards forum.
This standard enables the following capabilities:
a) CHS addressing with an 8.4GB limitation;
b) Logical Block Addressing (LBA);
c) removes the requirement of using interrupt 41h/46h to point at the Fixed Disk Parameter Table
information;
d) makes location and configuration information available to operating systems that do not use the BIOS to
access mass storage devices;
e) use data structures that apply to both IA-32 and IA-64 compatible architecture systems;
f) use data structures that can address media capacities for the next 20 years; and
g) boot from CD or DVD.
Requests for interpretation, suggestions for improvement and addenda, or defect reports are welcome. They
should be sent to the NCITS Secretariat, Information Technology Industry Council, 1250 I Street NW, Suite 200,
Washington, DC 20005-3922.
This standard was processed and approved for submittal to ANSI by National Committee for Information
Technology Standardization (NCITS). Committee approval of this standard does not necessarily imply that all
committee members voted for approval. At the time it approved this standard, NCITS had the following
members:
Editor’s Note 1: Insert INCITS Membership List Here
Technical Committee T13h on ATA Interfaces, that reviewed this standard, had the following members and
additional participants:
Dan Colegrove, Chair
Jim Hatfield, Vice-Chair
Mark Overby, Secretary
Editor’s Note 2: Insert T13h Membership List Here
Introduction
This standard encompasses the following:
Clause 1 describes the scope.
Clause 2 provides normative references.
Clause 3 provides definitions, abbreviations, and conventions.
Clause 4 is the overview.
Clause 5 is INT 13h functions limited to 8GB if disk addressing.
Clause 6 is INT 13h functions not limited to 8GB of disk addressing.