The CompactFlash Association has released the final physical and logical specifications of CFexpress 4.0, doubling the theoretical throughput of CFexpress 2.0 while maintaining the same form factors.
The CompactFlash Association (CFA) is one of those organisations that you've probably never heard of that touches a surprising number of areas of your life. It's the organisation that sets the spec for media including CompactFlash, CFAST, XQD, and more, and its new spec for CFexpress 4.0 represents a big leap, doubling the theoretical throughput of CFexpress 2.0 while maintaining the same form factors.
CFexpress was developed in 2016, and CFexpress 4.0 is an evolutionary specification riding on the success of 2019's CFexpress 2.0, employing the (now) industry standard PCI Express (PCIe) Gen4 bus and NVM Express (NVMe) 1.4c logical interface for even higher performance and more efficient NAND Flash access. The adoption of PCIe Gen4 is the critical factor here, and it's this that will give the new cards double the throughput performance compared to the PCIe Gen3 of CFexpress 2.0 while maintaining backwards compatibility.
That means the common Type A and Type B cards will peak at a theoretical maximum of 2GB/s and 4GB/s respectively. Peak read and write speeds of the current generation of CFexpress 2.0 cards tend to be around the 90% and 80% mark respectively, so in reality we'll be below those marks. But a 3600MB/s read and and a 3200MB/s write for the new CFexpress 4.0 Type B cards will be an interesting prospect when they get to the market, hopefully before the end of the year.
Crucially, CFexpress 4.0 will allow seamless migration from CFexpress 2.0 by utilizing the same underlying bus and logical interfaces of PCIe and NVMe while maintaining the exact same form factors. Here are the details.
The CFA is also preparing a new specification for VPG (Video Performance Guarantee) for higher sustained video recording which shall be released in the near future.