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Adam_J_3
Beginner
326 Views

Disabling Hardware Prefetch and Adjacent Cache Line Fetch in Sandy/Ivy Bridge without BIOS Support

Hi, I have 2 computers with sandy bridge-e and ivy bridge processors respectively and neither one them have BIOS options for disabling hardware prefetch and the adjacent cache line fetch options.

Is there any way (i.e. a MSR, etc) to disable these options in the processor?

Thanks!

Adam

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5 Replies
Bernard
Black Belt
326 Views

Sometimes access to some MSR registers is locked even  from kernel mode.If I am not wrong some functionality can be accessed by switching to SMM mode.

Patrick_F_Intel1
Employee
326 Views

Hello Adam,

Currently there is no publicly available method to enable/disable the hardware prefetchers using MSRs.

I'm checking whether the folks who control this info will reconsider that policy now that (at least some) BIOSes aren't providing an enable/disable prefetcher option.

I don't know when I will get a reply back.

In order to build the case for disclosing the settings, can you describe the reasons why you'd like to enable/disable the prefetchers?

Pat

Bernard
Black Belt
326 Views

Hi Pat,

does it mean that such a access (through MSR) is possible, but is only aavailable for Bios vendors?

Adam_J_3
Beginner
326 Views

I'm a graduate student researcher using your processors as a test bed for a paper we're trying to get published. I need the system to be as quiet as possible and I believe that the prefetcher might be introducing variability in our results.

I ended up buying another motherboard that supports disabling the prefetchers, but I'd still prefer to do it from linux (and to be able to test if the prefetcher is enabled easily from linux).

Bernard
Black Belt
326 Views

>>>I ended up buying another motherboard that supports disabling the prefetchers, but I'd still prefer to do it from linux (and to be able to test if the prefetcher is enabled easily from linux).>>>

I do not think if you can do it from kernel mode.Some of the low level functionality of CPU is accessed through the Bios which may switch to SMM mode of operation.

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