microSD Express memory cards to support up to 2GB/s data transfers

SD Association (SDA) has announced the new SD 9.1 specification that doubles the speed of microSD Express memory card speed up to 2GB/s, defines four new SD Express Speed Classes to ensure guaranteed minimum sequential performance levels, and adds support for multi-stream access and related power and thermal management to assure the guaranteed performance.

We first covered the microSD Express cards in 2019 as they were added to the SD 7.0 specification with promises of SSD performance through a PCIe 3.0 interface delivering up to 985MB/s. Over four years have passed since then, and I have yet to write about devices supporting the new standard, but the SD Association is not giving up with the introduction of the SD 9.1 specification that doubles the speed of the microSD Express cards, and full-size SD Express card can even reach close to 4GB/s.

microSD Express 2GB/s

More specifically, the maximum speed achievable on microSD Express over a PCIe Gen4 x1 interface will be 1,969 MB/s. The new cards remain backward compatible with the existing microSD card standard at the lower UHS speeds, while the PCIe interface is enabled by new pins as can be seen in the diagram above.

SD Express Classes 600MB per secondThe new SD 9.1 specification also defines four SD Express classes with minimum guaranteed speeds with the E150 (150 MB/s), E300, E450, and E600 pictograms that will be found on microSD and SD Express cards sold in the future.

Three new features for the SD Express Speed Class specification 9.1 have also been defined:

  • Power Management through Maximum Power (MP) values as defined by the host device
  • Thermal Management where the card indicates a group of its specific thermal thresholds.
  • Access Rule for Multi-stream Recording to ensure the minimum defined performance of the PCI/NVMe interface in SD Express cards, including multi-stream access of up to eight streams

Additional details may be found in the press release and a white paper about the new features added to the SD 9.1 specification. I also had a quick look at “microSD Express” cards on Amazon, and none showed up, with the results showing CFExpress cards instead, so while several companies have announced microSD and SD Express cards, they don’t seem to be commercially available just yet. Adoption will take a while and it’s unclear whether those types of SD cards will ever be broadly adopted.

Thanks to TLS for the tip.

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Anonymous
Anonymous
7 months ago

Reporting in 2020 suggested that microSD cards would be permitted to hit 2 GB/s (1969 MB/s) using PCIe 4.0 x1:

theregister.com/2020/05/20/sd_card_spec_version_8/

But then you read the whitepaper from that time and it said “A microSD Express with PCIe 4.0 is not supported, yet”. I could have sworn that “support” was announced before now.

petapixel.com/2023/10/19/sd-express-got-an-update-but-it-still-wont-make-the-format-work/

microSD is on the decline in smartphones, and seems to have been displaced by CFexpress in cameras. SBCs? RPi 5 is only finally adopting SDR104 speed. I guess it’s relevant in handheld consoles.

I dream of big, fast 128 TB microSDUCs that don’t melt.

dave
dave
7 months ago

Yep! Few phones have microsd as they now have lots of storage. Larger cameras are indeed adopting cf express type b. Cf express type a card are available from more manufacturers now, not sure if point-and-shoot small cameras have started to adopt those or not.

David Willmore
David Willmore
7 months ago

Has anyone ever seen a PCI-E SD card of any make? They’ve had several generations of these specs, but has anyone shipped a product? Accordingly, has anyone seen a device (other than a read/writer) that supports them?

As others have mentioned, digital cameras have pretty much gone to C.Fast cards.

Jack
Jack
7 months ago

Other than release more and more standards of the SD, I think the SDA should force or promote the benefits of using the high speed carda on the smartphones / electronic appliances. In 2023 I still barely found the UHS-II SD supported devices, not even the SD express one.

I’m still using the smartphone that support the expandable storage, but not happy to see the vendors that removing this feature from high end phones, as they have the excuse that the low speed of the card causing the system instable.

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