When CompactFlash was first designed, devices and applications didn't really exceed the read-write speeds of the first generation cards. This changed as digital camera resolutions grew, and uses of CompactFlash in embedded systems and other speed dependent devices became common. There are two main factors in how fast a CF card can write and read data. The first is the flash memory cells themselves. The second is the IDE controller chip on the card, which coordinates reads, writes, erasure, error correction, etc. As flash memory and more importantly controllers have gotten faster, CF cards perform much better. Vendors like Lexar Media, Inc. began using a the same speed rating that CD-RW manufacturers use to designate the speed of CD Burners with 1X being a write speed of 150KB/sec. The following is a table of common CompactFlash card write speeds.

When used with devices that have high throughput requirements like high resolution digital cameras, the high speed cards make a significant difference. Typically read speeds are even faster than the rated write speeds. Unless a very high performance factor is necessary, 45X cards currently provide the best performance to price ratio.

• CF cards are available in capacities from 16MB to 12GB. The CF Specification can support capacities up to 137GB.
• While many CF applications can operate with low capacity CF cards, higher capacity cards are increasingly used as digital camera resolution rises.
  

• CompactFlash cards support both 3.3V and 5V operation and can be interchanged between 3.3V and 5V systems. This means that any CF card can operate at either voltage. Other small form factor flash cards may be available to operate at 3.3V or 5V, but any single card can operate at only one of the voltages

• The connector used with CompactFlash is similar to the PCMCIA Card connector, but with 50 pins. Years of field experience in portable devices have proven the reliability and durability of this connector in applications where frequent insertions/ejections of the card are required. Other small form factor flash cards use connector technology that is not reliable or durable.

• CompactFlash provides the lowest cost flash storage solution. With the built-in controller, a wide variety of low cost flash technologies can be used. The built-in controller lowers costs further by allowing defective cells to be mapped out, thus increasing flash chip yields and by reducing costs in the host device.

• CompactFlash cards are able to withstand extremely rapid increases or decreases in temperature. Industrial version CompactFlash cards are offered with an extended operating temperature range of -40 C to +85 C.

• CompactFlash cards have an operating shock rating of 2,000 Gs, which is equivalent to a 10-foot drop. With typical usage, a CompactFlash card can be used for more than 100 years with no loss or deterioration of data.

• Typically consuming less than five percent of the power than that required to operate 1.8" and 2.5" disk drives, CF cards run at 3.3V or 5V with a single power supply. This makes them ideal for a range of current and next-generation, small-form factor consumer applications.

• Numerous platforms and operation systems support CompactFlash and the PCMCIA-ATA standard, including DOS, Windows 3.x, Windows 95, , Windows 98, Windows CE, Windows 2000, Windows ME, Windows XP, OS/2, Apple System 7, 8, 9 & OS X, Linux and most types of UNIX.

• CompactFlash data is protected by built-in dynamic defect management and error correction technologies.

As with PC Card, the Type I/II designation only has to do with the thickness of the card. Type I cards are 3.3mm thick, while Type II or 5.0mm thick. Both are 43mm in width and 36 mm in height. A Type I card will fit into a Type II slot or adapter, while the converse is naturally not the case.