class speed ratings

[sndcj1]

Forgive my ignorance, but does anybody understand the relationship between the new class speed ratings and the old 10x 40x 133x ratings? I was looking at a class 4 SDHC card (minimum 4MB transfer) and right next to it, there was a 133x card (20 MB sustained), and couldn't tell if these were comparable cards, or not. I realize 20 is bigger than 4, but as sustained doesn't necessarily mean it will give you a minimum of 4MB, and 4MB minimum doesn't imply less than 20MB sustained, does anyone have real world experience with this?

Thanks

 

[thr33face]

i don't know exactly, but doesn't 'sustained 20MB/sec' mean that the card is speced to transfer at a minimum of 20MB/sec?

 

[sndcj1]

Well, the odd thing is the new spec only has 3 speeds as of now, class 2, 4, and 6. I guess I don't quite understand why they would have a spec class for essentially a 13x card. I have seen class 2 devices, but the slowest card I can find these days is 40x. It seems as though there is something stricter about the spec, but I can't seem to find anything that compares a class 2 to a 40x card.