SD cards are one of the most popular data carriers on mobile devices. We currently have two standards – SDHC and SDXC for the normal version and micro. Now they will be joined by a third format called SDUC (“ultra capacity”). This will make these seemingly small gadgets fit a huge amount of data.
The SD Association has just announced the latest SDUC format specifications. This solution will certainly please people who record movies and take a lot of pictures. SDUC cards will have up to 128 terabytes of capacity. The new cards will increase the capacity by 64 times compared to the previous maximum SDXC capacity of two terabytes.
SDUC Technology behind such high data storage?
What’s more, the cards will be marked with “Express”, which means that the data flow will be at the level of 985 megabytes per second. For comparison, high-speed SSDs such as Samsung 860 Pro has a transfer rate of 520 – 560 MB/s (learn more from the PCLab test). SD Express is a PCIe interface that is implemented in the SD card controller. Interestingly, the new solution will not be available only for SDUC, but also for the previous ones.
It is not known yet when we will see SDUC Express cards on the market or how much they will cost. It is certainly not going to be a small amount of money. If you are interested in very large cards, the largest consumer SD card has 512 GB. We will also buy such a card in Poland. However, we need to be prepared for a considerable amount of expenditure.
Visually, an SD Express card looks like a UHS-II/III model because there are two PIN rows. The lower one is used for PCIe, so there is no compatibility with UHS-II. An SD Express card can use the upper row for UHS-I and can be written or read at up to 104 MByte per second in existing devices.
As usual, a 3.3-volt and a 1.8-volt rail are used, but the new SD 7.0 specification also provides 1.2 volts for additional form factors. The SD Association has also planned two additional PINs for the future to increase efficiency and performance. NVMe drivers are required for an SD Express card; current operating systems have had them for years anyway.
Price and Availability of SDUC SD cards
In addition to the number of commands transmitted simultaneously and their rearrangement, the functions of NVMe also include HMB (Host Memory Buffer): manufacturers can save themselves comparatively expensive SRAM for the controller on the SD Express card and buffer the Mapping table in the DRAM of the host system, among other things. Toshiba has a similar approach to the RC100 SSDs.
In addition to SD Express, the SD 7.0 specification also includes SD Ultra-Capacity (SDUC): The standard provides up to 128 TByte of capacity, previously it was 2 TByte per SDXC (SD Extended Capacity).
Partners such as Western Digital and Sandisk have already developed controllers for SD Express cards and shown prototypes, so the first models should be released in the coming months. When reading devices are to be expected remains open.
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