SD Express: Memory cards with 900 MB/s and 40,000 IOPS introduced

The new SD Express memory card standard with PCIe connection ensures an increased speed. Performance of up to 900 MB/s should thus already be possible in the slowest version, even if only for the read speed.

SD Express cards launch in 2022

Already at the beginning of the year, Phison officially presented its own SD Express platform with PS5017 controller. In April 2021, competitor Silicon Motion (SMI) also followed suit with the unveiling of the SM2708 controller, which follows in a similar vein. Now Lexar and Adata want to be the first manufacturers to offer correspondingly fast SD Express memory cards starting next year.

SM2708 works with PCIe 3.0 x2 and comes to a gross data rate of 1,969 MB/s (minus overhead) and that with a maximum user data rate of 1,700 MB/s. In operation with PCIe 3.0 x1, a speed of 900 MB/s should still be achieved. Phison is also supposed to achieve similar values with the PS5017 controller.

This slowest model will be the prelude for the new SD Express memory cards in the coming year and thus trumps already available UHS-II SD cards by a multiple. These theoretically reach a maximum of 300 MB/s.

First cards in benchmark test

The website The SSD Review has already been able to test a pre-production model of the new memory cards with SM2708 controller. The 256 GB memory card was tested with the help of a prototype SD Express card reader including a Realtek RTS5261 controller.

In the ATTO Disk Benchmark, the SD Express card achieved a maximum transfer rate of 857 MB/s in read and 394 MB/s in write and thus almost reaches the targeted value, at least in read performance. In CrystalDiskMark, a sequential transfer rate of 895 MB/s (read) and 411 MB/s (write) was achieved.

When asked by the testers, the manufacturer SMI confirmed that the test sample was equipped with 2-plane NAND memory. However, the final variant should then be equipped with 4-plane NAND and achieve a similarly high speed in writing as the current read speed values.

40,000 random IOPS possible

When using applications directly from the SD card memory, the Random 4K performance with random accesses to many small files is more interesting, which is measured in IOPS (Input/Output Operations Per Second).

Here, the SD Express card achieves around 40,000 random IOPS and thus calculates around ten times as fast as currently available SD cards, which is an immense performance gain. However, it remains to be seen whether the faster SD cards will actually be suitable as external storage solutions for programs in the future. After all, standard SATA SSDs already achieve a twice as high IOPS value.