what i s cpu prefetching?

[bitts]

hi,
there is an option on my motherboard named "cpu prefetching" which is disabled by default, should i enable it or leave it?
and under it is another option named "IO prefetching" also disabled, should i enable it or not?
i searched the net but dint get any decent answer...

thanks

 

[EarthDog]

Sorry for the google copy/paste... I had no idea and found this in a quick search.

http://dl.acm.org/citation.cfm?id=279529

 

[bitts]

Sorry for the google copy/paste... I had no idea and found this in a quick search.

http://dl.acm.org/citation.cfm?id=279529

ya i found it too.. but can you understand what its saying?
it went over my head..

 

[RGone]

From you link "EarthDog" > Under the best circumstances, i.e., with a significant investment in extra hardware, prefetching can significantly improve performance. For implementations without adequate hardware, prefetching often decreases performance.

It would be left disabled on my consumer motherboard for sure.

 

[bitts]

From you link "EarthDog" > Under the best circumstances, i.e., with a significant investment in extra hardware, prefetching can significantly improve performance. For implementations without adequate hardware, prefetching often decreases performance.

It would be left disabled on my consumer motherboard for sure.

so my H/W is adequate or not

 

[RGone]

Not.

 

[bitts]

K so disabled it is

 

[ssjwizard]

It could be worth testing. During my searching I came across discussions involving prefetching mostly in server forums.

I feel it necessary to point out that the IEEE paper that link makes reference to was written in 1998 and a 16byte memory bus is only 128bits so....

I havent read it completely yet but I found THIS much more recent write up on CPU cacheing.

 

[jmdixon85]

Mmm, makes me wonder if "hardware prefetching" should be enabled on my dual P4 HT 3.2Ghz fileserver?.....

 

[mikeyw]

I just ran a few tests of my work (mass parallel matrix multiplication, basically linpack) and got slightly (5%) slower times with hardware pre-fetching off.

I guess for gaming the difference may not be so pronounced but that's a nice boost for me

 

[RGone]

I just ran a few tests of my work (mass parallel matrix multiplication, basically linpack) and got slightly (5%) slower times with hardware pre-fetching off.

I guess for gaming the difference may not be so pronounced but that's a nice boost for me

But you are on an Intel platform and there are differences.

 

[mikeyw]

Oh my mistake I didn't realise I was in this forum! Clicked on a direct link

 

[RGone]

Oh my mistake I didn't realise I was in this forum! Clicked on a direct link

Not a problem by me. Just know caching is different for Intel and AMD.

 

[bitts]

It could be worth testing. During my searching I came across discussions involving prefetching mostly in server forums.

I feel it necessary to point out that the IEEE paper that link makes reference to was written in 1998 and a 16byte memory bus is only 128bits so....

I havent read it completely yet but I found THIS much more recent write up on CPU cacheing.

according to this page prefetching should drastically increase the performance of a system(older PC though).. but now that we have L3 cache this should be different now, this got me into another confusion

we need better understanding of CPU prefetching..!!!!

 

[bitts]

may be i should run "mikeyw"s test too... will run it as soon as i get time...

 

[RGone]

Try it on then off and make up your own mind with the software you use. It really is that simple.