Macbook Virtual cores


Dave_R

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I have a late 2009 Macbook Pro. with Snow Leopard

Model Name: MacBook Pro
Model Identifier: MacBookPro6,2
Processor Name: Intel Core i7
Processor Speed: 2.66 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache (per core): 256 KB
L3 Cache: 4 MB
Memory: 8 GB
Processor Interconnect Speed: 4.8 GT/s
Boot ROM Version: MBP61.005D.B00
SMC Version (system): 1.58f17
Serial Number (system): W80273RQAGW
Hardware UUID: 21476C6E-6E40-5585-93A1-A14F80F7EEC0
Sudden Motion Sensor:
State: Enabled

This model has hyperthreading capability giving an additional 2 virtual cores.

Hyperthreading on Snow Leopard can be turned off using "sudo nvram SMT=0"

Does anyone know how to find that this has worked? "About this MAC" only shows physical information.
 
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Lufbrarunner

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Open a 'Terminal' window, enter sysctl hw.physicalcpu hw.logicalcpu.
Which will print out the number of Virtual and actual cores.
 
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Dave_R

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Thanks - tried both - 4 cores showing as active. looks as though the sudo command doesn't work.
Will have to try Xcode.
 

Cory Cooper

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Hello and welcome.

Just curious...is there a particular reason you are attempting to disable the i7's Hyper-Threading? From what I remember, the sudo nvram SMT=0 command only worked on actual multiple CPU Macs like the Mac Pro (Xeon), and not single CPU Macs like the MBP. And, I thought it worked with Lion or Mountain Lion, and not Snow Leopard?

C
 

Dave_R

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Thanks for the reply & interest.

I picked up on the sudo command from MacRumors where it was said that it didn't apply to Lion & later. There wasn't any mention of only working on multiple processor models.

As to why, I'm running climate change simulations on the Macbook (dedicated) which are highly CPU intensive so thought that disabling HT might be more efficient and wanted to test the idea. ( And I mean really CPU intensive)
 

Dave_R

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In case anyone is interested, I've turned off HT using Xcode. I think the last version for Snow Leopard is 3.2.6 although some say 4.2 works as well?. To download this version I had to enable my Apple account as a developer with Two-Factor Authorisation.
The download is available via https://developer.apple.com/download/more/?name=Xcode.

The terminal commands are :-
hwprefs -v cpu_ht=false - to turn off

hwprefs -v cpu_ht=true - to turn back on

Using Cmd 3 in the Activity Monitor shows which cores are active (Thanks Lufbrarunner)

Also Cory, thanks for the info..
 
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Cory Cooper

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No worries...glad you got it resolved. Thanks for posting the solution for future use by others.

Be well,

C
 

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