hyperthreading....

[Carruth, Rusty]

In my past experience, I had noticed that the BOGOMIPS reported on (each of the) hyperthreading enabled CPUs was half that of the same CPU with hyperthreading turned off.  Which made me believe that the 2 CPUs were effectively half the speed of the single one.  (That is, if single is 2 bogomips, then hyperthreaded it was 1 bogomips on each CPU).

 

Since I knew that Linux did a good job of true multitasking, I always turned it off (assuming that part of the impetus for the whole thing was that Windows did a TERRIBLE job of true multitasking (remember trying to do ANYTHING else while doing a floppy format? Yeah, I thought you did J) so that windows could tie up one of the ‘CPUs’ doing a floppy format (or whatever) and still look responsive to the GUI using the other ‘CPU’.

 

So, I have to ask a few questions:

 

1 – does that slow 1.2GHz (SLOW? 1.2G? Wow, how times have changed!) play back fine with hyperthreading turned off?

2 – if XBMC gives a 20% performance boost on a CPU that is running at half the speed, is that really a performance boost overall?  (I’m probably missing something…)

 

Just wondering J

 

Rusty

 

From: plug-discuss-bounces at lists.phxlinux.org [mailto:plug-discuss-bounces at lists.phxlinux.org] On Behalf Of Bryan O'Neal
Sent: Sunday, May 04, 2014 9:48 PM
To: Main PLUG discussion list
Subject: Re: hyperthreading....

 

Short answer is that it is a way each physical core gets presented to the OS as two logically cores. Through some well documented voodoo it increases paralization for some work loads. Available on many Pentium systems since the Pentium 4 but also requires comparable chipsets so some early systems had processors that supported it but still could not use it. Mostly I see it on Xoen systems
Some bios allow you to disable it. 

On May 4, 2014 9:35 PM, "Michael Havens" <bmike1 at gmail.com> wrote:

what is it and is it an option in a modern BIOS?

I ask because I got an interesting message on another list othat I participate in.

[quote]Even though an AGP card may not support vdpau acceleration, a p4 should be able to use the Nvidia driver to get some openGL 2D accelerated output for XBMC. You should also have hyperthreading turned on in the BIOS, so the system will see two CPU cores, as XMBC will take advantage of that for maybe a 20% performance boost. My netbook, with a slow 1.2 GHz hyperthreaded Intel Atom CPU and 945M graphics, is still able to play back 720p h.264 encoded movies smoothly on MX 14.


Steve (finishing up the packaging of XBMC 13.0, which coincidently was just released)[/quote]

:-)~MIKE~(-:


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