PCIe REF_CLK outputs on the Elkhart Lake - are they HCSL?

[PaulS1]

I am trying to find what type of transmit driver/buffer is used for the PCie REF_CLK outputs on the "Elkhart Lake" processors. Is this HCSL or LP-HCSL or some other buffer type?

[Diego_INTEL]

Hello @PaulS1,

Thank you for contacting Intel Embedded Community.

I looked for this some time ago, it seems there is not mentioned in the documentation from newer families, like Tiger Lake or Elkhart Lake, but older families used HCSL.

In Elkhart Lake, document #599710 - PDG, we have this:

"Clock Request: Serial Reference Clock request signals for PCIe* 100 MHz differential clocks"

As a reference, for older families I have found the following:

For Denverton, document #558578 - PDG.

Or in Apollo Lake, document #563002:

"HCSL(Host Clock Signal Level) is differential signal type used for the 4 PCIe reference clock: PCIE_CLKOUT[3:0]P/N."

I hope this helps.

Best regards,

@Diego_INTEL