Even the fastest SD cards are still quite slow. This poses a great challenge for 8K video recording, handheld PC gaming, and other technologies that continually demand greater data transfer speeds and improved storage reliability. So, to remediate the problem, the SD Association has announced its new SD 9.1 specification, which achieves a data transfer rate two times greater than any existing SD card.
Source : SD Card Speeds Will Double with New SD 9.1 Specification
