SanDisk announced high-capacity microSD and SD cards with a claimed capacity of 200 MB/s. This seems to defy the UHSI standard. These cards are capable of transferring 200 MB/s despite using UHS-I specifications that limit speed to 104 Mb/s.
The latest release from the company features microSD and standard SD cards with capacities up to 1TB. This is not unusual. However, these cards are unique in that they promise up to 200 MB/s read speed and 140 MB/s writing speeds on the 256GB-to-1TB capacities.
PetaPixel’s complete guide to memory cards explains that there are two types of SD and microSD memory card: UHSI and UHSII. UHS-II uses Low Voltage Differential Signing Technology, which allows for speeds of up to 312 Mb/s. UHS-I has only one row of pins, so it can read at 104 Mb/s.
If SanDisk’s cards only support UHS-I, then how is it possible that they can move data faster than the SD Association’s specs? It’s a little tricky.
SanDisk QuickFlow Technology
QuickFlow, a new technology developed by SanDisk, allows it to use the SD Association’s UHSI specification in its original implementation and add enhancements to make it more efficient.
SanDisk created custom firmware that included detection schemes and adjustments to the clock, bus and card output timing. SanDisk claims it samples data at both the rising and falling edges and raises the clock frequency to 208 MHz. This allows for transfer speeds that are twice as fast than standard UHSI cards. This is combined with faster memory core interfaces, a NAND memory with proprietary high performance trims.
This card is capable of performing faster in certain situations, but it is still compatible with UHS-I host devices.
This is why cards are only rated V30 (another term explained here in the memory card guide). The cards can only reach the maximum speeds promised when they are inserted into compatible host devices. This usually means that the card must be inserted into a SanDisk memory reader. The cards will not be able perform at the UHSI spec of maximum 104 MB/s (though they are often much lower).
It is possible that cameras could be upgraded to support SanDisk QuickFlow. This would enable the new memory cards perform at their promised speeds.
SanDisk has also released a Pro Reader, which supports these maximum transfer speeds. This reader will allow data to be transferred off cards much faster than UHS-I cards. This reader can also be used with the company’s Pro Dock 4.
UHS-I: Some Advantages
These UHS-I cards have a benefit: they can hold larger capacities than UHS-II cards. They are currently limited at 512GB and only available by Wise and ProGrade Digital. Also, they are much cheaper. ProGrade Digital’s new UHS-II SD card, which holds 512GB UHSII memory cards can be as high as $500. SanDisk’s UHS-I cards offer a more affordable option.
Prices for the SanDisk Extreme PRO UHSI SD cards range from $19 for 64GB to $280 for 1TB. Prices for the SanDisk Extreme PRO UHS–I microSD cards are also varied. The 64GB option retails at around $20, while the 1TB option is priced at approximately $330.