Most optical drives today are combo CD/DVD drives that support all the DVD and CD formats. The speeds of the drives are rated by their DVD-ROM and CD-ROM transfer rates. The original DVD drive (1x) transferred data at 1.39MB per second, sufficient for movies. By doubling the spindle RPMs, the data transfer rate increased to 2.77MB/sec (2x) and so on.

**Nine Times the CD-ROM Rating**

Each DVD X is equivalent to roughly nine X's of CD speed because a DVD 1x is 1.39MB and a CD-ROM 1x is 150KB. See DVD player and CD-ROM drives.

**A Lot of X's**

Each DVD X is equivalent to roughly nine X's of CD speed because a DVD 1x is 1.39MB and a CD-ROM 1x is 150KB. See DVD player and CD-ROM drives.

DVD-ROM DataDVD-ROM Transfer RateX Rating (MBytes/sec)1x 1.39 2x 2.77 2.4x 3.32 4x 5.54 6x 8.31 8x 11.08 10x 13.85 12x 16.62 16x 22.16 18x 24.93 20x 27.70 22x 30.47 24x 33.24

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