Searching for cpu capabilities? Look at /proc/cpuinfo...

Most of us know, that with

cat /proc/cpuinfo

the number of cpus, cpu speed, cpu model etc. can be found. But there is one interesting line which is called flags:

processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 13
model name : Intel(R) Pentium(R) M processor 1.73GHz
stepping : 8
cpu MHz : 1733.000
cache size : 2048 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss tm pbe bts est tm2
bogomips : 3457.11
clflush size : 64

Ok, the acronyms sound familiar. Here the outputs from some other cpus:

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 pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr dca sse4_1 sse4_2 popcnt lahf_lm ida
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 pbe constant_tsc pebs bts pni monitor ds_cpl cid xtpr

Hmmm. No flag like 64Bit or x64... How can this acronyms be decoded?
Let's ask the kernel sources!
There is one file inside the sources, where all this flags are defined:

arch/x86/include/asm/cpufeature.h

Here are the most interesting ones:

#define X86_FEATURE_HT (0*32+28) /* Hyper-Threading */
#define X86_FEATURE_LM (1*32+29) /* Long Mode (x86-64) */
#define X86_FEATURE_VMX (4*32+ 5) /* Hardware virtualization */
#define X86_FEATURE_PN (0*32+18) /* Processor serial number */

Just if you are not sure about installing 64Bit Linux, check for lm. And if ht is shown, you do not worry, can detect twice as much cores as there are, or if...