u1 vs u3 SD card

How differs the u1 from the u3 SD card ?

The sigle u refers a type of bus interface for memory card. You find also the acronym UHS for this class. u1 refers to UHS-1 and u3 refers to UHS-3.

To resume, the u3 class is  »able » to provide a maximum speed largely stronger than the u1 class. But be aware , the notion of U speed class is a maximum speed, it isn’t the effective speed use in reality or effectively use by the device. it isn’t too a minimum speed guarantee.

The u1 card use only one row of pin, so the data traffic between upload and download is share on the same row of pin.  On the contrary, the u3 class use two lane for data transfer in his default mode, by using two rows of pins. One lane is use for transfer data from the host to the card and the other lane is use for transferring data from the card to the device. So the device can reach a faster speed rate.

The u3 (UHS-3) can reach a maximum speed of bus of 624 Megabytes per second.
The u1(UHS-1) can reach a maximum speed of 104 Mb per second.

u1 u3
maximum bus speed MB/s 104 MB/s 624 MB/s
Type of cards SDHC, SDXC, SDUC SDHC, SDXC , SDUC

You can find the u1 and the u3 class in the follwing types of SD card :  SDHC, SDXC and SDUC.

reference :
https://www.sdcard.org/developers/overview/bus_speed/index.html

https://www.sdcard.org/developers/overview/speed_class/index.html

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