[LAU] How to turn off hyperthreading?

Simon Wise simonzwise at gmail.com
Tue Mar 26 05:31:59 UTC 2013


On 26/03/13 06:25, John Murphy wrote:
> On Mon, 25 Mar 2013 22:05:42 +0100, Jeremy Jongepier wrote:

>
> I just don't get the fear of UEFI?
>

Because UEFI is designed to prevent hardware being booted unless it is into an 
unmodified and signed OS version, and this hardware lock can be set up so it 
cannot be turned off, and for some devices (eg non intel tablets) microsoft (for 
example) will only certify them if they are locked this way to run only 
microsoft signed software. So most windows tablets can never be loaded with 
anything not signed by microsoft ... that is they can now be "trusted" not to 
have anything else running on them ... for example something modified by the 
person who thinks they own the device, perhaps linux, perhaps a patched windows, 
perhaps some system not so compliant with the demands of media distribution 
companies as the standard windows is.

Fortunately this would be a major pain to windows users on a PC, since older 
versions wouldn't boot ... but given windows on a tablet is new, and a much more 
locked down device than a PC, and perhaps also that the hardware manufacturers 
of tablets are more willing to go down this path than PC manufacturers, then 
this is applied to tablets (where they can probably get away with it) but not 
PCs. For intel devices microsoft does not require UEFI to be set so it can't be 
turned off, for non-intel tablets it does. So Linux is locked out of any such 
devices.

Not good if you like to run linux, so don't buy windows tablets of course ... 
and be very cautious of UEFI on any device since it means you no longer have 
control of hardware you thought you had bought and now own. What you do with it 
is limited by what the UEFI settings let you do, and in some cases you are 
unable to change these settings.


Simon




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