Looking for more memory cards for my DSLR, I divided deep into the CF specification, history, and marketing. It's a mess. Here I've focused on the SanDisk CF cards, as that's what I usually get. More specifically, I wanted to know, which name or specification corresponded to which speed, and what I could expect from the that card when taking a lot of pictures, e.g. hundreds of pictures as part of a panorama.
Over at Digital Photography Insights, Rob Galbraith already has very extensive tests with different cards. Currently, only the EOS 5D Mark III list is covering most relevant CF cards, but tests with the Canon 50D is also planned. Looking forward to it. Also of interest from his page is the various card readers. This led me to the Addonics ADSACF which connects the CF reader directly to the internal SATA bus, and achieves read speeds of more than 90 MB/s. At ~$30, it looks like a very good buy.
Before digging into the SanDisk cards, a bit of background and relevant documents. The CF specification is guarded by the CompactFlash Association, and you have to buy the detailed docs, however they've started applying some cute icons to each of the more recent versions. Still, it does not tell you a lot about the read/write speed; e.g. the CF 5.0 and 6.0 specifications carry the same icon. Wikipedia has a bit more detail on the older CF specifications. It mentions that the first CF revisions were using PIO (Programmed input/output); PIO mode 2 since the beginning in 1995, and mode 4 in 2003, with DMA 33 in 2004. According to Rob Galbraith, several of the cards implement dual protocols, i.e. both PIO and UDMA. I've not been able to verify this anywhere else, but it seems to make sense, for backwards compatibility. Of course, when operating in PIO mode, one will not be able to take advantage of the speed the newer cards are rated for.
Current CF cards are based on PATA mode, so the UDMA (Ultra Direct Memory Access) modes apply. I've lifted he relevant table from the current Wikipedia article, as shown below. Of some relevance is also the speed rating used for SD cards. Here the "x" rating is based on the CD-ROM transfer speeds, e.g. 6x means 6 * 150 kB/s, or 900 kB/s. Some of the Lexar, Kingston, and other CF also use this in the name of the cards, but not SanDisk.
|Mode||Number||Also called||Maximum transfer rate (MB/s)||Defining standard|
|7||Ultra ATA/ -||-||-|
Back to the SanDisk cards, though. SanDisk itself is not very good at keeping old product pages around, so a lot of the references I found was at Digital Photography Review; they keep their articles around. The story starts in 1994, with SanDisk defining the CompactFlash standard, batteling it out with other companies and cards like Miniature Card, SmartMedia, and later MMC/SD, various Memory Stick formats, and xD-Picture Card.
The first article I can find on dpreview, is an updated product range of "larger capacity CF cards of 64MB, 80MB and 96MB". No mention of speed, but another article from the same date talks about 1.4 MB/s as high-speed. Later on, the different product lines have been overlapping, upgraded, and renamed, and thus adding a lot of confusion. Add to that strange "marketing" products like the 2007 "Ducati Edition" (4 and 8 GB cards at 45 MB/s), and the terrain starts to get difficult to navigate. Also note, the "Extreme" line has two incarnations, its inital series from 2003, which was just called "SanDisk Extreme", and the newer UDMA versions; not sure which year they were introduced. The same is the case for the initial "Ultra" line.
Below I've listed the SanDisk CF product lines I could find, with best effort searches for largest size, and guesses at standard / IO mode. The model prefixes where partly from Amazon, with hints from the Nikon approved cards page. Feel free to get in touch if you have further information.
|Ultra||??||2.8 MB/s||512 MB||PIO 2||2001||dpreview|
|Extreme||??||6 MB/s||1 GB||PIO 2||2003||dpreview|
|Ultra II||SDCFH||9 MB/s||8 GB ?||PIO 4||2004||dpreview|
|Extreme III||SDCFX3||20 MB/s||16 GB||PIO 4 /
|Extreme IV||SDCFX4||40 MB/s||8 GB||PIO 4 /
|Extreme III||SDCFX3||30 MB/s||32 GB||PIO 4 /
|Extreme IV||SDCFX4||45 MB/s||32 GB||PIO 4 /
|Ultra||SDCFH||30 MB/s||16 GB||PIO 4 /
|Extreme||SDCFX||60 MB/s||32 GB||PIO 4 /
|Extreme Pro||SDCFXP||90 MB/s||64 GB||PIO 4 /
|Extreme Pro||SDCFXP||100 MB/s||128 GB||PIO 4 /