The SD Association recently released the SD Express 9.1 specification, which defines newly upgraded standards for vendors manufacturing SD cards and supporting hardware. The new requirements include PCIe 4.0 and NVMe architectures, which could double maximum speeds to 2GB/s.
Additionally, the 9.1 specification introduces a new labeling system to indicate which speed class each device requires and what each SD Express card supports. The four tiers (pictured below) represent minimum read/write speeds ranging from 150MB/s (like SanDisk’s recently announced 1.5TB card) to 600MB/s. Customers must check a product’s packaging or instruction manual to ensure they use the right card for each device.