MIL-HDBK-9660 Dod Produced Cd-Rom ProductsThis document was prepared by the Defense information Systems Agency DISA, in cooperation with the services and other activities within the Department of Defense DOD. The goal of this document is to provide information and guidelines to support the creation and interoperability of Compact Disc-Read Only Memory CD-ROM development and use within DOD. This document specifies core compact disc fundamentals for the DOD community. It is strongly recommended all DOD components comply with the fundamentals established within this document. Specialized functions within DOD may require expanded internal guidance to meet their own mission needs. All other Government entities are invited to use this document.

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 - 26 - 27 - 28 - 29 - 30 - 31 - 32 - 33 - 34 - 35 - 36 - 37 - 38 - 39 - 40 - 41 - 42 - 43 - 44 - 45 - 46 - 47

MIL-HDBK-9660B

APPENDIX A

ADDITIONAL INFORMATION USEFUL FOR CD PRODUCERS AND USERS

A.1 SCOPE

A.1.1 Scope. This appendix adds some additional information that may be useful for producers and users of CDs. This appendix is for guidance only.

A.2 APPLICABLE DOCUMENTS

This section is not applicable to this appendix. A.3 DEFINITIONS

The definitions in section 3 of this handbook apply to this appendix. A.4 GENERAL INFORMATION

A.4.1 General. Compact Disc (CD) was the first commercial success using laser technology for digital recording (Video Laserdisks came first but used analog recording). Almost all computers shipped today are equipped with CD drives.

A standard CD physically consists of a thin reflective layer (usually aluminum), on top of a polycarbonate substrate, covered by a protective overcoat. It is 4.72 inches in diameter (120 mm) and is single-sided.

CLV (Constant Linear Velocity) recording is used to maximize data density throughout the disc. To keep the data passing under the read head at the same rate, the disc rotates faster towards the inside of the disc and slower towards the outside. The first single-speed CD drives (1X) had a rotation speed of 539 rpm (revolutions per minute) on the inner tracks and 210 rpm towards the outer tracks. These changes

in disc rotation slow access time and lower data transfer speeds. Single-speed drives transferred data at

153.6 KBps (kilobytes per second).

Data transfer speeds and access time can be improved by spinning the disc faster. Double-speed drives (2X) transfer at 300 KBps, triple-speed (3X) at 450 KBps and quad-speed (4X) at 600 KBps. Multimedia applications demand at least a 2X transfer rate, most are optimized for 4X. Expect a 1.2 MBps rate for an BX (spinning as fast as 4,000 rpm) and 1.5 MBps for a 10X. 12X, 16X, and higher drives are already available. However, access times remain somewhere between 150-250 msec (milliseconds), still far slower than magnetic hard drives.

CAV (Constant Angular Velocity) is a newer recording technique that rotates the disc at a constant speed. The number of bits in each track is the same, but density varies because inner tracks have smaller circumferences. This method wastes disc space, but allows for much higher spin rate speeds. Some drive manufacturers use a combination CLV/CAV for optimal performance and reliability. A 12X basic spin rate (i.e., the maximum mechanical rotation at the inner tracks) drive at full CAV provides effective speeds of up to 30X.

CD drives can be internal (installed into a drive bay in the computer's chassis), or external (has its own power supply). The interface for connecting the CD drives to the computer can be SCSI, SCSI-2, IDE, EIDE, or proprietary. NOTE: SCSI or SCSI-2 interface is used for CD recorders.