The Linux Kernel Begins Preparing Support For SD Express Cards

Written by Michael Larabel in Hardware on 24 July 2020 at 08:20 PM EDT. 27 Comments
Announced earlier this year was the SD Express specification offering around 4x the speed of existing SD cards thanks to leveraging PCI Express 4.0 (or otherwise PCI Express 3.0 fallback) and the NVMe 1.4 protocol. The Linux kernel has begun preparing for SD Express compatibility.

SD Express aims to deliver nearly four gigabytes per second for data transfers thanks to leveraging PCIe and NVMe. SD Express is coming to SDHC, SDXC, and SDUC memory cards. These new SD Express cards that are expected to begin hitting retail channels in the months ahead do offer backwards compatibility with the legacy SD interface. In fact, the devices are initialized at first through the legacy SD interface. Following the legacy initialization process, the MMC host and SD card are both checked for PCIe and NVMe support. If both sides support the upgrades, then the new interfaces are utilized.

The Linux kernel's MMC code has begun preparing this initial support for SD Express with that basic infrastructure handling. No new hardware support is introduced but just the fundamental checks for SD Express via PCI Express and SD Express 1.2V handling. Expect more to come on the SD Express for Linux support front in the weeks/months ahead.
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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

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