Hi,
Check the APIC bypass de assert message bit. 0x5b bit3 I think you need to put there 0.
There are some registers from 0x70 - 0x7f documented in the Programming guide only. 0x7c bit 3 is hypetrtransport mode for APIC put 0 there.
And 0x77 bit 5 I dont understand what exactly it is. Try flipping it too.
Rudolf