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Why do I see 8 cores on 1 quad core processor

Posted on 2014-12-02
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Last Modified: 2014-12-02
Hi all,

maybe I don;t understand: Why do I see 8 cores on 1 quad core processor?

Please see attachment.
CPU.jpg
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Question by:Agrippa
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6 Comments
 
LVL 14

Expert Comment

by:John-Charles-Herzberg
ID: 40475671
The i7 family is a Quad-core processor that has 8 threads. Normal quad-cores have 4 threads, and since hyper-threading is enabled, your computer recognizes those 8 threads as processors.

Hyperthreading is a form of simultaneous multi-threading that takes advantage of super scalar architecture. Multiple instructions operating on separate data in parallel. They appear to the OS as two processors, thus the OS can schedule two processes at once. In addition two or more processes can use the same resources. If one process fails then the resources can be readily re-allocated. The OS must support simultaneous multi-threading (SMT).

More good information is at:

What Does “Dual Core” & “Quad Core” Mean? [MakeUseOf Explains]
http://www.makeuseof.com/tag/what-does-dual-core-and-quad-core-mean-makeuseof-explains/
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Author Comment

by:Agrippa
ID: 40475691
Hi John,

thankx for the info. The problem is that this is a server processor (see attachment right pane. I have an application which cannot run on more than 4 cores, since I am not able to point out 4 cores to the application I need to make sure that Windows does not see more that 4 cores.

Do you have any idea how to fix this?

Disable HT?
Any way to appoint 4 cores to the app?
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LVL 14

Accepted Solution

by:
John-Charles-Herzberg earned 300 total points
ID: 40475695
I think what you need to do is disable Hyperthreading in the BIOS.  The attached video might help get you going.

https://www.youtube.com/watch?v=7rscmqrFWac

Thanks
JC
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LVL 70

Assisted Solution

by:garycase
garycase earned 100 total points
ID: 40475729
As noted above, all you have to do is disable hyper-threading in the BIOS and you'll only be using the 4 actual cores.

Hyper-threading in essence is simply a complete separate set of registers for each core so switching between two threads is nearly instantaneous (no registers save/restore as in a typical multi-processing task switch).    Since the implementation is in hardware, it "looks" like 2 cores to the underlying OS ... but the performance of each of these hyperthreaded cores is only half of the actual performance of the core (actually a tiny bit less than half).

There are some applications that run very poorly when hyper-threading is enabled, so it's designed to be disabled when desired -- and virtually every BIOS will support this option.
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LVL 35

Assisted Solution

by:Seth Simmons
Seth Simmons earned 100 total points
ID: 40476433
here is more information on the CPU you are running; others have already commented on the HT portion which you see in the list of features of the processor you have

Intel® Xeon® Processor E5530
http://ark.intel.com/products/37103/Intel-Xeon-Processor-E5530-8M-Cache-2_40-GHz-5_86-GTs-Intel-QPI
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Author Comment

by:Agrippa
ID: 40477641
Thankx guys!

I disabled the option: logical processor in the BIOS, which I guess stands for HT. Now in Windows I can see 4 cores, which makes the APP working now, great!

Thankx again
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