SD card speed class standards are prone to changing. It may seem confusing, but it reflects the speed with which the technology behind them is improving. The latest improvement is SD Express 8.0, introduced in 2020 to address anticipated shifts in the market such as increased speeds of mobile computing and the transition of flash memory to PCIe NVMe from SATA.
SD8.0 offers options that previous hardware does not. Higher capacity thresholds (potentially as much as 128TB), and higher read and write speeds, as well as power and thermal management optimized for those higher speeds. It also offers multi-lane support for PCIe and interfaces with PCIe NVMe 4.0. What does that mean? In essence, SD Express 8.0 is compatible with a high-bandwidth, low-latency protocol and supports infrastructure intended to limit bottlenecking. When paired with an SD Express Gen4x2 host, those speeds can be as high as 3,938MB/s read.
To recognize and more easily categorize the capabilities of this new SD generation, a new speed class, SD Express Speed Class was created. Superior to Speed Class, UHS Speed Class, and Video Speed Class, it measures SD cards by minimum sequential write speed. Cards with a speed of 150MB/sec receive an E150 logo. Other logos include E300, E450, and E600.
The SD Express 8.0 is suitable for multiple purposes, such as high-performance mobile computing and handling high-resolution content such as burst mode photos, 8K video, gaming, IoT, etc. At the time of writing, there is little hardware that supports SD Express 8.0. The Nintendo Switch 2 is the most high-profile device currently compatible with the standard. However, its usage will likely contribute to the further proliferation of the format as formats that make good use of its capabilities grow in popularity.
