Soon you can buy SD Express cards that offer throughput of up to 985 MB / s thanks to the new SD Version 7.0 specification. The new specification provides support for PCIe and NVMe interfaces to increase performance, and also supports devices with a capacity of up to 128 TB. That's the jump over the current 2 TB limit.
985 MB / s throughput for a simple SD card may seem ridiculous, but video, VR, automotive use cases, and higher-resolution IoT applications are increasingly entering the performance limits of today's products.
OEMs are notoriously slow to develop radically new designs, so the new SD Express specification is also backward compatible with the old UHS-I interface. Backward compatibility means that the end devices will come to market faster, while others will wilt on the tendrils due to the reworked interfaces that prevent wide acceptance.
The specification has reserved space for new pins for future use, so there is also room for forward progress (PDF). The specification also provides power consumption of up to 1.8 W, which improves performance. The NVMe 1.3 protocol also provides some new features for SD cards, such as the Host Memory Buffer (HMB), which provides a small portion of system memory for performance enhancement, and multi-queue support, which improves performance at the same time File transfer improved.
The SD connection will initially interface with SDHX, SDXC and SDUC cards, but plans to provide a fast connection to MicroSD cards in the future. The first cards with the improved interface are expected to hit the market in 2019.