The Canon EOS 1D-X is UDMA 7 enabled.
The Canon EOS 7D, EOS 50D, EOS 1D Mark IV and the EOS 5D Mark II can be UDMA 7 enabled though a firmware upgrade.
Canon EOS 7D firmware upgrade »
https://www.usa.canon.com/internet/portal/us/home/support/details/cameras/eos-dslr-and-mirrorless-cameras/dslr/eos-7d/eos-7d?subtab=downloads-firmware
Canon EOS 7D, EOS 50D, EOS 1D Mark IV and the EOS 5D Mark II firmware upgrade »
https://www.the-digital-picture.com/News/Default.aspx?Cat=Canon-Firmware-Updates