There are two form factors for CompactFlash devices, named type I and type II. Both have a footprint of 42.8 mm x 36.4 mm, but they vary in thickness: type I cards have a height of 3.3 mm, while type II reach 5.0 mm. All CompactFlash memory cards are type 1 models, while 1” hard drives such as the IBM/Hitachi Microdrives were built as CF type II products. All type I cards can be used in type II slots, but not vice versa.
In addition to the two CF form factors, there have been several revisions of the interface. All CF cards are based on an IDE or UltraATA interface, but the effective performance depends on the interface speed and the flash memory technology. Finally, your host controller has to be fast enough as well. The real beauty of CF is that you can buy a 32 GB card and run it in a 10-year-old CF device—just at reduced performance. You could also take your decade-old CF card and insert it into a brand new SLR camera; the card may just be too slow for continuous shooting.
The earliest CompactFlash specifications were based on programmed I/O (PIO), but these were replaced by the faster Direct Memory Access (DMA) method with the introduction of the CompactFlash 3.0 standard in 2004.
|CF 1.0||1994||ATA-1PIO Mode 2||8.3 MB /s||Compact Flash+ standard for I/O cards|
|CF 2.0||2003||ATA-2PIO Mode 4||16.6 MB/s||128 GB max. capacity|
|CF 3.0||2004||UltraDMA / 66||66 MB/s||25 MB/s throughput in PC Card slots, password protection|
|CF 4.0||2006||UltraATA / 133||133 MB/s||137 GB max. capacity|
CompactFlash cards are currently available in sizes up to 32 GB, but 64 GB capacities have already been announced. Typical capacities for hobby photographers are 4, 8, or 16 GB; we recommend going for at least 8 GB. If you intend to shoot uncompressed RAW photos on your digital SLR camera, or RAW plus JPEG, you should definitely look for the fastest cards on the market. So let’s get started.