NEC Express 5800 User Manual page 294

Hardware
"Disabled." The parameter that is changed by you is maintained even if the HW
configuration is modified after that. Refer to appendix C "Settings for each OS" for
x2APIC setting details.
(Note 5) The parameter "C6" is displayed when the processor supporting this function is
embedded.
(Note 6) The parameter cannot be set to "Enabled" when "Intel(R) VT-d" parameter in Intel(R)
VT for Directed I/O Configuration menu is set to "Disabled."
(Note 7) The parameter cannot be set to "Disabled" when "Intel(R) TXT" parameter in Intel(R)
TXT Configuration menu is set to "Enabled"
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