btrimmer - 2005-07-28 7:29 PM
Well, I don't know this for sure, but based on the number of electrical contacts you can see on the card
(50 pins for CF versus about 10 for SD
), my guess would be SD is a serial I/O device. CF is definately parallel
(16-bit data, right??
). Now granted, speed isn't determined just by the number of data lines; you have to consider the bitrate per data line too. But I suppose that could have something to do with SD not performing as well as CF, particularly under sub-optimal conditions.
Then again, I could be way off here...
You are absolutely right, SD cards are based on Serial IO. CF cards support ATA interfaces, which can be pretty speedy. Howevery, serial io interfaces like USB
(yes, USB is based on serial IO, think Universal
Serial Bus
, can reach up to 12Mbps for USB 1.1 and 48Mbps for 2.0.
Granted, these are theoretical speed and mostly can be achieved only in burst mode, still should be fairly fast.
In that sense, any SD can outperform a slower speced CF card, it all depends on the speed rating of the card.