DUAL CF CARDS OVER PCI? pic.twitter.com/p54tO3BqCF

— foone (@Foone) February 21, 2022

This is for booting up virtualization OSes like the VMWare OS with redundancy, so if one card fails the other one takes over transparently.

Have used these very often. Extremely useful and much faster/cheaper than a spinning or SSD drive, especially when SSDs were new.