microSD Express announced with up to 985MB/s speeds, better power effiency

Less than a year after the SD Express standard was announced, the fast PCIe-based technology has come to the tiny microSD form factor. It will use the second row of pins of UHS-II style cards to enable NVMe v1.3 connectivity.

microSD Express cards will deliver speeds of up to 985MB/s. For comparison, the fastest UHS-I cards go up to just over 100MB/s, the fastest UHS-II push that to a bit more than 300MB/s.

With support for the low-power sub-states (L1.1 and L1.2) of PCIe v3.1, the new cards will actually use less power than classic microSDs, despite being much faster than them.

The Express standard is great at multitasking, so there will be no performance hit to moving apps to external storage. To achieve this, the microSD Express cards borrow a few tricks from PC SSDs.

• Multi Queue Support: each CPU core can store commands for the card in the host RAM, the cards will read and execute them
• Host Memory Buffer: this is a feature from SSDs without on-board DRAM that allows them to use the host RAM for cache
• Bus Mastering: this feature enables the ones above, by letting the card to access the host RAM (DMA); actually, this has other uses as it allows things other than the CPU (e.g. modem, camera, etc.) to send data to the storage device

Here’s a 3-minute video from the SD Association that introduces the new standard.

Now for some bad news – as we said, the microSD Express standard requires the extra UHS-II pins. And we are yet to see a phone that supports UHS-II cards. Still, watch out for microSD cards with the “Express” logo in the near future. Maybe phone makers will finally have a reason to upgrade their microSD slots (the ones that still have them, that is).

PS. the cards will be backwards compatible with existing microSD slots, but obviously you'll lose the NVMe speeds.

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