Alongside their SD 7.1 specification, the SD Association has revealed its MicroSD Express standard, upgrading the humble SD card with PCIe connectivity and NVMe as its upper layer protocol. In short, the performance if NVMe SSDs is coming to the world of MicroSD cards, while also offering backwards compatibility with older standards like SD and SD-UHS104.

What changes with MicroSD Express is that the second row of pins from UHS-II cards is repurposed to support PCIe 3.0 x1 connections, with the new standard utilising the NVMe protocol to offer transfer speeds of up to 985MB/s. This change will allow future SD cards to provide transfer speeds that surpass SATA Solid State Drives, which is an amazing feat given the small form factor of MicroSD cards.

In effect, this breaks backwards compatibility with UHS-II and UHS-III devices, though UHS speeds of up to 104MB/s can still be utilised. With MicroSD Express, speeds of up to 985MB/s are possible, which is great news for future high-performance mobile devices.

Support for NMVe 1.3 also adds several SSD-like specifications to the SD Express standard, like bus mastering, multi-queue, host memory buffer and several other enhancements while maintaining backwards compatibility with SD UHS104 and lower standards.

Because of the SD Associations repurposing of UHS-II pins with SD Express, the standard is not backwards compatible with either UHS-II or UHS-III speeds, preventing UHS-II/III cards from accessing their full speeds on SD Express hosts and SD Express cards from saturating UHS-II/III hosts, reverting to UHS104 speeds. A full chart which showcases backwards compatibility is available below.

PCIe Specification conformance tests are available today for SD Express, thanks to a collaboration between PSI-SIG and the SD Association.

While transfer speeds of 985MB/s seem excessive for a MicroSD card, it is encouraging to see compact storage solutions offer more SSD-like features and increased transfer speeds, especially in an era where 8K video recording is becoming more popular and high-resolution/framerate video is becoming recordable on today’s smartphones and drones.

This new standard will provide additional competition in the high-end video production market, though SD Express will also be usable for future mobile computing platforms, games consoles, automotive applications and a wide range of other applications.

You can join the discussion on the SD Association’s MicroSD Express standard and its 985MB/s transfer speeds on the OC3D Forums.