Sat 03-Aug-13 12:11 PM | edited Sat 03-Aug-13 01:53 PM by dagoldst
> >What matters in practice is the sustained write speed of the >"system" (the combination of card and camera).
I agree with your statement, but ... the SD input/output chip is the governor of absolute speed from the card to the camera image processing engine. The testing at the beginning of this post confirms that and happens to align with thom hogan's original test. I had an email exchange with him some months ago on this very subject. lol
Edit to add
I did a bit of research on how SD moves data to understand the chips on the Inrevium link better - to be specific, we are dealing the the TE4302RXPF chip, which is in fact, clocks at 100Mhz. That Does NOT mean it can move 100Mbytes/second. It means that that chip can move 50Mbytes/sec. Here is why.
At 100Mhz, the chip transfers 4 bits of data per clock cycle. For those that do not know, it takes 8 bits to make a byte, so two clock cycles are needed. Hence the data transfer rate is half the clock rate with this particular chip.
If everything is perfect on a given card and it TRULY meets the UHS-1 spec, etc, it will move data at 50Mbytes per second.
It may be that Sandisk is somewhat overrating the Extreme Pro card that the OP used in the test. Also, it is quite possible that even a 1/8 of a second of error in the measurement is skewing the results of the file transfer measurements. 1/8th of a second would equal another 6.25Mbytes of data transferred and adding that to the observer 39.5 would equal 45Mbytes/second, or, exactly what Sandisk claims.
"Extraordinary claims require extraordinary proof " - Carl Sagan