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Is the Micro SD U3 or U1?
#1
Does U3 micro Sd cards make a difference according to U1?

Is there a noticeable difference in Linux systems?
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#2
(03-13-2019, 06:30 AM)kardanadm Wrote: Does U3 micro Sd cards make a difference according to U1?

Is there a noticeable difference in Linux systems?
Of course it does. You could be less lazy and read the wikipedia article, that has a very clear explanation of these classes. Basically it's a UHS-I related speed classification and it requires that U1 cards garanteed at least 10 MB/s minimum read/write speed, whereas U3 - 30 MB/s. The difference.

As of "difference in Linux systems", it depends on how good the linux support of an SD host controller is. I guess linux can do UHS-I, so it should be able to deliver to user what card is capable of. kinda. Finally, because the question is in the RockPro64 subforum, it should be noted, if I remember correctly, that current Rockchip's SoCs expose the limit on the clock speed to the SDMMC/EMMC controllers of 150 MHz, compared to the standard limit of 200/208 MHz (eMMC/SD respectively). That gives the maximum throughput (read) of around 75 MB/s. I saw results for RockPro64 and Asus Tinkerboard close to that number. Some cards (even U1) claim to be able to achieve up to 90 MB/s. Such cards could get the most of the Rockchip SoC based SBCs in terms of speed (any). These numbers depend solely on the internal efficiency of the card, not the interface speed limit (which is always higher than the former). Anyway, rk3399 is capable of SDR104 mode (the fastest one, but not the most balanced by speed/energy efficiency ratio, DDR50 is such, also supported by the controllers and all the micro SD form factored UHS-I cards by the way too) and RockPro64 has UHS-I implemented properly. So, given the practical limit of 75 MB/s by the SoC frequency, you would be better to go with a good U1 card, they are cheaper than U3. Speaking of the 150 Mhz limit for the Rockchip SoCs, it's yet to be figured out, is it possible to up it to the normative and standard 208 MHz. Stability issues maybe are the preventer. It's Rockchip, who needs to answer that question.
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#3
Thank you for quite detailed information
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