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The following two command seems to give me different information about the same hardware

srs@ubuntu:~$ cat /proc/cpuinfo | grep -e processor -e cores
processor   : 0
cpu cores   : 4
processor   : 1
cpu cores   : 4
processor   : 2
cpu cores   : 4
processor   : 3
cpu cores   : 4

srs@ubuntu:~$ sudo dmidecode -t processor 
# dmidecode 2.9
SMBIOS 2.6 present.

Handle 0x0004, DMI type 4, 42 bytes
Processor Information
    Socket Designation: LGA1155
    Type: Central Processor
    Family: <OUT OF SPEC>
    Manufacturer: Intel            
    ID: A7 06 02 00 FF FB EB BF
    Version: Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz       
    Voltage: 1.0 V
    External Clock: 100 MHz
    Max Speed: 3800 MHz
    Current Speed: 3300 MHz
    Status: Populated, Enabled
    Upgrade: Other
    L1 Cache Handle: 0x0005
    L2 Cache Handle: 0x0006
    L3 Cache Handle: 0x0007
    Serial Number: To Be Filled By O.E.M.
    Asset Tag: To Be Filled By O.E.M.
    Part Number: To Be Filled By O.E.M.
    Core Count: 4
    Core Enabled: 1
    Characteristics:
        64-bit capable

Until today I thought I had a single processor with 4 independent cores. I also thought that within each core can be used different threads.


Mitch has given to the way to find out that I have got the Single socket Quad Core (Example 3):

srs@ubuntu:~$ cat /proc/cpuinfo | grep -e processor -e "model name" -e "cache size" -e "physical id" -e "siblings" -e "core id" -e "cpu cores"
processor   : 0
model name  : Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz
cache size  : 6144 KB
physical id : 0
siblings    : 4
core id     : 0
cpu cores   : 4
processor   : 1
model name  : Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz
cache size  : 6144 KB
physical id : 0
siblings    : 4
core id     : 1
cpu cores   : 4
processor   : 2
model name  : Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz
cache size  : 6144 KB
physical id : 0
siblings    : 4
core id     : 2
cpu cores   : 4
processor   : 3
model name  : Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz
cache size  : 6144 KB
physical id : 0
siblings    : 4
core id     : 3
cpu cores   : 4

Now I can understand that there are much more different kinds of processors that I never thought. Thanks

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1  
The wording of your question (especially at the very end) suggests that you are familiar with the difference between processors and cores. Are you asking something specific about how the terms are used in dmidecode? You may want to edit the question to clarify (or maybe reword the title a little bit). –  Eliah Kagan Aug 29 '12 at 9:19
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2 Answers 2

up vote 3 down vote accepted

A multi-core processor is a single processor that have more than 1 cores running at same speed.

Dual CPU = Means 2 physical CPU's

Dual Core = Means that a single CPU that have two cores allowing it to deal with two threads at once

For example, a Quad Core Processor that runs at speed of 3GHz , will have 4 cores running at that speed. What that means that at a given time the CPU can process data 4 times in 4 separate cores.

Newer applications and games are coded in a way that benefit from Multiore Processors.

For more information you can look at Understanding Linux /proc/cpuinfo

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Its a very useful information that let me understand that there are much more different kinds of processors that I never thought. Thanks. –  Salvador Aug 29 '12 at 10:10
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It should be noted that on recent hardware, your computer will often report twice as many cores as physically exist - (on this i7 4-core machine System Monitor shows 8, for example). This is due to Hyperthreading, present in most modern systems.

A hyperthreaded CPU can only execute one set of instructions at a time, but any given program tends to spend a lot of time waiting (for data to be fetched from memory, or other bits of hardware to do something) the CPU has multiple queues of instructions which can be switched between whenever one becomes idle. Thus, a single physical core is presented to the operating system as two virtual cores.

This is essentially the same as the operating system using threads to allow many programs to share a single processor, but being implemented as hardware rather than software is more efficient. The article above claims typical tasks on two virtual cores is about 30% faster than the equivalent work on one real core.

So, cat /proc/cpuinfo shows 8 processors, whereas dmidecode shows

Core Count: 4
Core Enabled: 4
Thread Count: 8

ie, 8 virtual cores and 4 real ones.

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According to my BIOS Intel HT Technology is not supported by my processor. –  Salvador Aug 29 '12 at 15:19
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