Xavier NX reference clock PCIe -output

When using the Xavier NX board as a PCIe x4 root port, what is the type of reference clock that outputs the Module? Is it LVDS or HCSL?

As you can see in the Design Guide: The PCIe REFCLK inputs and PCIEx_CLK clock outputs comply to the PCIe CEM specification “REFCLK DC Specifications and AC Timing Requirements.” The clocks are HCSL compatible.