topic x2apic on Xeon E5620 in Intel® Moderncode for Parallel Architectures

x2apic on Xeon E5620

chernikov_t — Tue, 27 Sep 2011 14:13:09 GMT

I have server PowerEdge R710 with two Xeon E560 CPUs on board. But when i check x2apic presence using CPUID(EAX=1) i got 0x29ee3ff value in ECX register which tells me that local x2apic functionality is not available (bit 10 is not set). This check is made right after entering into a protected mode. Is it a correct way to determine x2apic presence? Does mentioned processors have this functionality?

x2apic on Xeon E5620

chernikov_t — Wed, 28 Sep 2011 06:38:59 GMT

Oops... Typo in my mesage: of course I check 21st bit, as it mentioned in "Intel 64 Architecture x2APIC
Specification" (318148.pdf). But 0x29ee3f & (1 << 21) == 0

x2apic on Xeon E5620

chernikov_t — Tue, 04 Oct 2011 13:08:39 GMT

It seems that Xeon 5620 CPU have strange behaviour: while cpuid tells that x2apic is not available it still report that directed EOI support is present. So all what i have to do is just check x2apic presence and do not try to enable directed EOI with disabled x2apic even if APIC version register report that directed EOI is supported.

Thanks all :)