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Re: PAE or not PAE?

On Monday 12 March 2018 15:27:23 Hans wrote:

> > Note that the non PAE kernel in older Debian versions up to Jessie
> > lacked multi-processor (including multi-core and hyper-threading)
> > support.
> Yes, I read this, too. The N280 is a single core, but mith
> hyperthreading, I have two cores.
> Is this still so, that the non-pae-kernel lacks still hyperthreading,
> or does it do today, too?
> And second question: Is PAE preferred (with the look to speed) or
> better use non-pae?
> Cheers
> Hans

Both pae and hyperthreading take time, hyperthreading quite a bit more 
than pae. With hyperthreading, to switch to the 2nd task, takes a 
complete processor state stored on the stack, the stack pointer reloaded 
to point at the image of the 2nd task, then pull the full register dump 
for task 2 back into the processor. Then and only then can the first 
cycle devoted to task 2 be initiated. Ditto to swap back. For boxes that 
will run a realtime task, the first thing we do is turn off the 
hyperthreading. Its a solution that works ok, but I can't think of a 
better way to make a decently fast cpu into a provable slowpoke. All it 
really does for us is to help heat the shop. You can keep it above the 
dew point with electric heat to help control rust, or you can enable 
hyperthreading and its exactly the same turns of the electric meter 
either way.  An excellent demo of the TANSTAAFL principle.

Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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