The CompactFlash Memory Card: CompactFlash (CF) Card standard

The CompactFlash Memory Card was introduced originally by SanDisk in 1994 these cards use a Parallel ATA bus and are available with capacities varying from 2 MB to 256 GB. The CompactFlash card is considerably larger than it's main competition the SD card and arguably a little more robust. It is important to know the maximum capacity CompactFlash your device can support before purchasing a card, for example Nikon's original D1 professional camera will only work with cards up to a 2GB maximum capacity - Larger than this will just not work!

 

The CompactFlash Memory Card: CompactFlash "CFast":
In 2008 a new Cfast variant of the CompactFlash  card was announced, these cards replaced the original Parallel ATA bus with a faster Serial ATA bus, this reflected the changes that was already happening with PC hard drives. These cards are quite rare and are not backwardly compatible with the original Parallel ATA bus standard devises.

The CompactFlash Memory Card: CompactFlash Reliability
When CompactFlash cards were first released in 1994 they used the best memory chips of the period, these needed to be powered at all times in order to maintain data storage whenever the card was not being powered up by the device, this was achieved with a non-replaceable internal battery, once the battery is exhausted the card is of limited use, also the NOR flash memory chips once used in the cards had a write/re-write life cycle of approximately 10,000. Current CompactFlash cards use superior NAND flash memory chips which do not need an internal battery and have an expected write/re-write life cycle of 1,000,000.

The CompactFlash Memory Card: CompactFlash Speeds:
CompactFlash cards often still refer to there speeds as a multiple of the data transfer speeds of the original Compact Disk, a CF card will often be marked as being x80, meaning the card is eighty times faster than the standard CD which is taken as 150 kB/s (normally rounded down to an easily remembered number ). Alternatively the output and input data transfer rates may be given in MB/s, if only one speed is shown it will normally be the read speed which is significantly faster than the write speed and looks most impressive.

The need for high speed cards is normally limited to video cameras and and high end HD professional digital still cameras with impressive continuous shooting rates. Originally CompactFlash cards used PIO memory mode but was changed to UDMA around 2005, the cards are backwardly compatible with PIO mode devices but will not be able to operate at their quoted UDMA speeds when forced to use their backup PIO mode. Continuous write speeds are less than the maximum transfer speeds so check your device's operational requirements before purchasing cards which may not be up to the task required, or are "overkill" and therefore more expensive than they needed to be.

 

Maximum
Transfer Rate

Memory Mode

 

Video Recording Capability Guide

 
5.2 MB/s PIO Mode 1
  X35 - Adequate for standard video recording.  
8.3 MB/s PIO Mode 2
  X50 - Adequate for 720p HD video recording.  
11.1 MB/s PIO Mode 3
  X75 - Adequate for 1080p/1080i HD video recording.  
16.7 MB/s PIO Mode 4
  X100 - Adequate for  1080p/1080i HD video recording and HD stills.  
20 MB/s PIO Mode 5
  X133 - Adequate for  1080p/1080i HD video recording and large HD stills.  
25 MB/s UDMA Mode 1
  X166 - Adequate for Real-time broadcasts + large HD video files + 3D video capture  
33.3MB/s UDMA Mode 2
  X200 - Adequate for Ultra HD 4K resolution digital television and digital cinematography.  
44.4MB/s UDMA Mode 3
  X300 - As above for recording but improved inter-device transfer speeds.  
66.7 MB/s UDMA Mode 4
  X440 - As above for recording but improved inter-device transfer speeds.  
100 MB/s UDMA Mode 5
  X666 - As above for recording but improved inter-device transfer speeds.  
133 MB/s UDMA Mode 6
  X900 - As above for recording but improved inter-device transfer speeds.  
166 MB/s UDMA Mode 7
  X1100 - As above for recording but improved inter-device transfer speeds.  

 
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