So you've got a really sweet system, but you want to know if it will run a 64-bit OS. Like 64-bit Linux, of course. Easiest way I've found to tell if your system supports a 64-bit OS is to check the output of /proc/cpuinfo. Specifically, check "flags" for "lm" (Long Mode):
(mark@skull)~> cat /proc/cpuinfo | grep -i -e processor -e flags
processor : 0
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm pni monitor ds_cpl cid cx16 xtpr
processor : 1
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm pni monitor ds_cpl cid cx16 xtpr
Notice the "lm" in the flags on each of the CPU's. If you see "lm" in the flags then your system will support an x86_64 kernel. If you don't see "lm", then you're obviously stuck in 32-bit land. In the kernel, this is defined in include/asm-x86_64/cpufeature.h ...
(mark@skull)~> cat linux-2.6.22/include/asm-x86_64/cpufeature.h | grep "Long Mode"
#define X86_FEATURE_LM (1*32+29) /* Long Mode (x86-64) */
(mark@skull)~> cat /proc/cpuinfo | grep -i -e processor -e flags
processor : 0
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm pni monitor ds_cpl cid cx16 xtpr
processor : 1
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm pni monitor ds_cpl cid cx16 xtpr
Notice the "lm" in the flags on each of the CPU's. If you see "lm" in the flags then your system will support an x86_64 kernel. If you don't see "lm", then you're obviously stuck in 32-bit land. In the kernel, this is defined in include/asm-x86_64/cpufeature.h ...
(mark@skull)~> cat linux-2.6.22/include/asm-x86_64/cpufeature.h | grep "Long Mode"
#define X86_FEATURE_LM (1*32+29) /* Long Mode (x86-64) */
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