I’ve tested many cards, the one comes with the BeagleBoard-XM is a class 4 card, which is giving average speed on the current shipped image ( Angstrom 2010.7-test-20110220 - Linux beagleboard 2.6.32 #3 PREEMPT ) , but when you go to develope and want real 1Ghz performance alike, I recommend you to change it and buy a Class10 uSD, or SD. a speed test I’ve done here shows 2 cards I’ve used one is 8GB oem brand called Team, and the other is Transcend class 10 too.
Using bench tool of http://crystalmark.info/, Watch the results !
If you want 'real 1Ghz' performance, run your processor at 1 GHz. SD
cards have no impact on processor clock rates.
Regardless, SD card class numbers are mostly meaningless for measuring
performance.
The class rating is a manufacturer applied rating that only measures
one specific type of operation of the card, specifically writing to
completely erased erase-blocks. This is the mode of operation that
video cameras sometimes use when recording.
Linux file systems, basically anything other than FAT, do not operate
like this. Thus, class is a useless rating for embedded systems.
More valid tests include measuring the number of open erase-blocks that
the card can sustain simultaneously in linear and random writes, as
well as determining performance at 4, 8, and 16 KiB write sizes.
A tool like flashbench[1] is a much better tool to compare cards than
class ratings.
[1]:http://git.linaro.org/gitweb?p=people/arnd/flashbench.git;a=summary
-Andrew
I knew andrew that processor clock doesn’t have something to do with the SD for sure, I’m talking about reading / writing data to SDs / OS loading all of them without good SD speed is slow !
