Your server includes a function called x2APIC, which is enabled by default, but must sometimes be disabled before installing some versions of Linux. The following table shows the versions for which it must be disabled.
Note - You must disable x2APIC before booting Oracle Hardware Installation Assistant. See Disable x2APIC Before Booting Oracle Hardware Installation Assistant (CR 7112255) for details.
For more information, refer to How to Access the BIOS Setup Utility in Sun Server X2-8 (formerly Sun Fire X4800 M2) Service Manual.