Browse Definitions:

X (compact disc access time)

Contributor(s): Steven Raimi

In compact disc ( CD ) and digital versatile disc ( DVD ) technology, X is a base multiplier that expresses the speed with which data could be read (the read access time) from the compact disc in its original version, which was 150 kilobytes (KB) per second. As successively faster CDs arrived, manufacturers adopted the convention of indicating the read time in terms of the original speed. Thus, a 2X CD had a read access time of 300 KB per second and so forth. Our table relates each common drive speed to its read access time. It also shows the range of revolutions per minute (RPM) used to make the read access time possible.

CD/DVD Drive Speed Maximum Data Transfer Rate RPMs (revolutions per minute)
1X CD-ROM 150 KB/sec 200 - 530
2X CD-ROM 300 KB/sec 400 - 1060
4X CD-ROM 600 KB/sec 800 - 2120
8X - 12X CD-ROM 1.2 MB/sec 1600 - 4240
24X - 50X 1.8 - 6 MB/sec 2400 - 6360 approximately
1X DVD-ROM 1.25 MB/sec No exact data, but much slower than 1X CD-ROM

There are only minor increases in read access time as one moves from the 24X, 32X, and 40X drives. Higher rotation speeds are (somewhat) prone to noise and vibrations and may cause performance to vary from drive to drive.

It seems unlikely, because of these vibrations and performance variations, that read access times will increase much above present levels. Even though a hard drive can reach much faster speeds of rotation, its enclosure stabilizes the entire mechanism and therefore avoids much of the noise and vibration inherent in the open CD-ROM drive.

This was last updated in September 2005

Start the conversation

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.


File Extensions and File Formats

Powered by:


  • risk map (risk heat map)

    A risk map, also known as a risk heat map, is a data visualization tool for communicating specific risks an organization faces.

  • internal audit (IA)

    An internal audit (IA) is an organizational initiative to monitor and analyze its own business operations in order to determine ...

  • pure risk (absolute risk)

    Pure risk, also called absolute risk, is a category of threat that is beyond human control and has only one possible outcome if ...


  • federated identity management (FIM)

    Federated identity management (FIM) is an arrangement that can be made among multiple enterprises to let subscribers use the same...

  • cross-site scripting (XSS)

    Cross-site scripting (XSS) is a type of injection security attack in which an attacker injects data, such as a malicious script, ...

  • firewall

    In computing, a firewall is software or firmware that enforces a set of rules about what data packets will be allowed to enter or...



  • business continuity and disaster recovery (BCDR)

    Business continuity and disaster recovery (BCDR) are closely related practices that describe an organization's preparation for ...

  • business continuity plan (BCP)

    A business continuity plan (BCP) is a document that consists of the critical information an organization needs to continue ...

  • call tree

    A call tree -- sometimes referred to as a phone tree -- is a telecommunications chain for notifying specific individuals of an ...


  • volume manager

    A volume manager is software within an operating system (OS) that controls capacity allocation for storage arrays.

  • external storage device

    An external storage device, also referred to as auxiliary storage and secondary storage, is a device that contains all the ...

  • NetApp SolidFire

    NetApp SolidFire is a business division of NetApp Inc. that specializes in all-flash storage systems.


  • hybrid hard disk drive (HDD)

    A hybrid hard disk drive is an electromechanical spinning hard disk that contains some amount of NAND Flash memory.