Compact Flash cards Speeds

Flash memory devices are non-volatile and solid-state, and thus are more robust than disk drives. Cards consume around 5% of the power required by small disk drives and still have reasonable transfer rates of over 45 MB/s for the more expensive 'high speed' cards.[6]

Card speed is usually specified in "x" ratings, e.g. 8x, 20x, 133x. This is the same system used for CD-ROMs and gives the data rate as a multiple of the data rate of the first CD-ROMs (i.e. the data rate of an audio CD). The base rate is 150 kB/s, so for example, 20x = 20 * 150 kB/s = 3.0 MB/s.

The following table lists some common ratings and their respective maximum transfer rates.
Rating Speed (MB/s)
6x 0.9
32x 4.8
40x 6.0
66x 10.0
100x 15.0
133x 20.0
150x 22.5
200x 30.0 EXTREME3
266x 40.0 EXTREME4
280x 42.0
300x 45.0
333x 50.0
400x 60.0
433x 65.0
600x 90.0 UDMA
667x 100.0