ASROCK Fatal1ty X399 Professional Gaming Serie Manual Del Usuario página 32

U.2 Connector
(36-pin U2_1)
(see p.1, No. 13)
28
This connector supports U.2
NVM Express storage devices up
to Gen3 x4 (32 Gb/s).
* If U.2 Connector is plugged,
M2_1 will be disabled.