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I want to know how many processors my ubuntu box has and if they are multicore. I did

cat /proc/cpuinfo  

and I see something like this

processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 15
model name  : Intel(R) Core(TM)2 Quad CPU    Q6600  @ 2.40GHz
stepping    : 11
cpu MHz     : 1603.000
cache size  : 4096 KB
physical id : 0
siblings    : 4
core id     : 0
cpu cores   : 4
apicid      : 0
initial apicid  : 0
fdiv_bug    : no
hlt_bug     : no
f00f_bug    : no
coma_bug    : no
fpu     : yes
fpu_exception   : yes
cpuid level : 10
wp      : yes
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 nx lm constan
t_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm lahf_lm dts tpr_shadow vnmi flexpriority
bogomips    : 4787.19
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

notably, I saw such data block four times from
processor : 0 to processor : 4
and each time I see

cpu cores : 4  

I want to know what does that mean?

Is this machine has 4 processors and each processor has 4-cores?

Please let me know

Thank you

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2 Answers 2

up vote 3 down vote accepted

The Q6600 is a single processor with 4 cores. You should actually be seeing processors 0-3 (total of 4) not 0-4 (which would be 5). If you look at the "physical ID" field you should see the same number (0).

On a hyperthread enabled quad-core, you should actually see 8 virtual processor cores (2 virtual HT cores run on each physical core). You may have hyperthreading disabled.

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can I enable hyperthreading? how? –  learner Oct 7 '11 at 19:27
    
If there is an option to disable or enable HT (and I bet there is) you will find it in the BIOS. It's a hardware setting. –  Mark Russell Oct 7 '11 at 19:36
2  
cool, i'll try it out, thanks Mark –  learner Oct 7 '11 at 19:53
    
Happy to help, and yes if you can reenable it, I would. There are extemely few situations where HT is not desirable. Good luck! –  Mark Russell Oct 7 '11 at 20:52

Check out the "lstopo" command in the "hwloc" package.

http://www.open-mpi.org/projects/hwloc/

http://packages.ubuntu.com/hwloc

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Welcome to Ask Ubuntu! Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. –  RolandiXor Oct 8 '11 at 20:20

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