Apple's fix for Intel's MDS flaw cripples performance on Mac

ozziej

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Jul 22, 2009
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654
Ugh, sloppy reporting again. It doesn't cripple the performance unless the user actively selects to disable hyper threading (which is Intel's suggestion to permanently fix the problem, but they don't recommend doing it), and the same issue will happen with Windows if you disable HT.
 

ekske1

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Apr 22, 2017
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Ugh, sloppy reporting again. It doesn't cripple the performance unless the user actively selects to disable hyper threading (which is Intel's suggestion to permanently fix the problem, but they don't recommend doing it), and the same issue will happen with Windows if you disable HT.
Only reporters can report? :unsure:
 

Fulcrum29

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Jun 25, 2010
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Uhm, Intel's patch in general cripples the CPU? Full mitigation, the recommendation made by Apple is to disable hyper-threading and to enable an additional CPU instruction as a preventative measure which may cripple the CPU up to 40% on Apple clients. I saw yesterday that some media outlets got the 40% number and made wild assumptions. Enabling the CPU instruction and disabling Intel HT is a choice on Apple clients.

Intel themselves said that patching and disabling hyper-threading will only cost you up to 9%, but this is a internal test with a i9-9900k CPU. Previous third-party tests have shown that low to mid end CPUs are the most impacted and that 2015 and pre-2015 CPUs are the worse cases.

Google is also disabling Intel HT on Chromebooks.

It is best to post, and not link to, the Intel PR article on this topic.
 

irBosOtter

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Feb 14, 2014
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2,710
Ugh, sloppy reporting again. It doesn't cripple the performance unless the user actively selects to disable hyper threading (which is Intel's suggestion to permanently fix the problem, but they don't recommend doing it), and the same issue will happen with Windows if you disable HT.

Think it's only Apple and a few other companies that sugested people disable hyperthreadding, Intel suggests you don't do that at all.
 

crysis

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Dec 22, 2006
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So if you don't disable hyper threading your computer is vulnerable? ok, got it!
 

Fulcrum29

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So if you don't disable hyper threading your computer is vulnerable? ok, got it!
Intel HT enabled = vulnerable
Intel HT disabled = less vulnerable

It is a preventative measure, but no cure.
 

Polymathic

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This not a good if you use your Mac for heavy tasks like video editing
 

Johnatan56

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Aug 23, 2013
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So either I can take a risk with HT enabled and have my work sped up a lot, or disable it and throw my laptop out the window due to frustratingly slow compile times? Sounds like a fun choice to make...
 

Fulcrum29

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So either I can take a risk with HT enabled and have my work sped up a lot, or disable it and throw my laptop out the window due to frustratingly slow compile times? Sounds like a fun choice to make...

It is a known exploit within lab conditions. There is no known evidence that this exploit has been used in the wild. No real case exists other than the pre-prepared PoC which doesn’t give any case to study other than illustration.

As we know, any OS is vulnerable. I’m sure Intel and many others are proactively busy with penetration testing. These tests will be protected by some parties and published by other parties.
 

Sinbad

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I bet apple regret moving away from powerpc architecture now
 
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