Tonight I searched the Internet for the meaning of the different card speeds. I came across the Windows Mobile Team Blog website which explains that: there is no standard to the speed of the cards! The important paragraph from this website reads:
"How about speed?
SD cards have all sorts of marketing names-Ultra, 133x, High Speed, etc. There's no standard for what these terms mean, so I can't tell you if an "Ultra" card is faster or slower than a "133x"one. But I can tell you that there are huge speed differences in different SD cards. A few years ago I did a simple test where I plugged an SD card into a desktop SD reader, copied 30M of files to it, timed the copy with a stopwatch, and then repeated the procedure with different cards. I literally found some cards that finished in 30 seconds while others took 80."
The above was posted on Friday, January 12, 2007 11:07. So it is an up-to-date message.
In performance tests I found on a particular website, the Sandisk and Sandisk Ultra II mini sd cards have the same av. read speeds! Only the av. write speeds are different!!
On another website an own brand 2GB 150x minisd was advertised as having a read speed of 12MB/s and write as 5MB/s. The same item also stated that the card had a High Read Speed- Up to 22mb/s, and a Write speed of up to- 7mb/s transfers. The other figures must be the average read and write speeds.
Another website advertises its own 2GB 133x mini sd card has the following minimum performance (Read 20 MB/s and Write 9 MB/s)
As you can see from the above, the performance of cards considerably varies. Basically do not believe the hype of the advertising e.g. 133x , 150x, Ultra etc. Investigate what the performance of the card is- the average and the minimum and maximum read and write speeds.
The new SDHC has a new category scheme and this can be found on the SD Association website.