Back in June 2018, the first SD Express cards were made official, based on the Secure Digital (SD) 7.0 specification. Fully backwards compatible, they immediately attracted attention for providing a speed close to GB/s adopting PCI Express 3.0 and NVMe 1.3 interfaces in card format, leaving in the mud any model available until then. Now comes the SD 8.0 specification for Express cards, which goes much further.
Just announced by the SD Association, Secure Digital 8.0 for SD Express cards will surpass them by incorporating the PCIe 4.0 specification and maintaining the NVMe Express protocol, providing maximum speeds of nearly 4 GB per second without losing backward compatibility with existing SD card compatible cameras, readers, and other devices.
The operation of the new SD Express cards is interesting, since they offer two high-speed modes. Cards that do not require maximum performance will be able to use two PCIe 3.0 or a single PCIe 4.0 channel for a maximum case rate of 2 GB/s, while higher speed cards will use two PCIe 4.0 channels to approach those coveted 4 GB/s. This, in turn, means that manufacturers will be able to sell two types of SD 8.0 express cards at distinctly different prices.
The cards will be offered in SDHC, SDXC and SDUC formats.