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](https://discussions.apple.com/thread/2421202?start=0&tstart=0) apply to your case? — harrymc, Sep 10 '12 at 05:42

score 3 · Answer 1 · answered Aug 29 '12 at 20:49

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 '12 at 20:49

Kale Muscarella

This method is disabled on sleep as well, thats why I asked a permanent method. – Sid Aug 30 '12 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 '15 at 01:56

Brian · Answer 2 · 2012-09-10T01:08:48.037

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=""

edited Sep 10 '12 at 01:08

answered Sep 10 '12 at 00:57

Brian

Resets on restart. Already tried this. – Sid Sep 13 '12 at 07:11
It shouldn't reset if you put it in the boot-args, @Sid . You must have skipped that step. – cutrightjm Sep 15 '12 at 20:44

2 Answers2