How to disable HyperThreading on Mac OS X Lion?

Question

Unlike my old Windows Boxes and Linux Boxes, I do not have access of something similar to a BIOS on my MacBook Pro.

I want to disable Intel i7's HyperThreading (so 4 cores look like 4 cores and don't try to simulate extra ones).

There are solutions for disable HT via developer tools temporarily, but I need something to do it permanently (one that does not reset on reboots).

This is for a MacBook Pro 15" Retina.

Does the last entry in this thread apply to your case?
– harrymc
Sep 10, 2012 at 5:42 — harrymc, Sep 10, 2012 at 5:42
Well, does it or does it not ?
– harrymc
Sep 14, 2012 at 20:17 — harrymc, Sep 14, 2012 at 20:17

Kale Muscarella · Accepted Answer · 2012-08-29 20:49:44Z

3

Download and install Xcode. It includes a Processor.prefPane (not sure where it's located exactly) that allows you to disable hyperthreading.

With Xcode installed, you can also disable hyperthreading using the following terminal command:

hwprefs cpu_ht=false

I don't believe this setting is retained after restarting your Mac, so you might want to create an AppleScript to run that command on startup.

answered Aug 29, 2012 at 20:49

Kale Muscarella

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This method is disabled on sleep as well, thats why I asked a permanent method.
– Sid
Aug 30, 2012 at 20:36
1

These no longer work on Yosemite: the hwprefs command is gone and the Processor.prefPane panel no longer loads.
– J. Peterson
Feb 14, 2015 at 1:56

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Brian · Accepted Answer · 2012-09-10 01:08:48Z

2

Any luck with the following? Requires a reboot to take.

$ sudo nvram SMT=0

Might be something you can put in boot-args as well but I couldn't find it.

$ sudo nvram boot-args=""

answered Sep 10, 2012 at 0:57

Brian

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Resets on restart. Already tried this.
– Sid
Sep 13, 2012 at 7:11
It shouldn't reset if you put it in the boot-args, @Sid . You must have skipped that step.
– cutrightjm
Sep 15, 2012 at 20:44

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2 Answers 2