Unconditional jump penalty on Pentium 
Author Message
 Unconditional jump penalty on Pentium

I know that a branch misprediction costs at least 5 cycles on Pentium. How
about an unconditional jump? Does it incur any penalty at all? Is there any
difference in a short unconditional jump vs. a long unconditional jump?
Thanks a lot.



Mon, 10 Jan 2000 03:00:00 GMT  
 Unconditional jump penalty on Pentium


Quote:
> I know that a branch misprediction costs at least 5 cycles on Pentium. How
> about an unconditional jump? Does it incur any penalty at all? Is there any
> difference in a short unconditional jump vs. a long unconditional jump?
> Thanks a lot.

Read all about it in Agner Fog's latest revision of his pentopt.txt
manual at either:

    http://www.geocities.com/SiliconValley/9498/p5opt.html

or

    http://announce.com/agner/assem

--
Paul Hsieh
http://www.geocities.com/SiliconValley/9498/mailme.html



Wed, 12 Jan 2000 03:00:00 GMT  
 Unconditional jump penalty on Pentium

Quote:

> Read all about it in Agner Fog's latest revision of his pentopt.txt
> manual at either:
>     http://www.geocities.com/SiliconValley/9498/p5opt.html
> or
>     http://announce.com/agner/assem

Thanks for pointing out the update, I've begun to migrate (30+K of)
changes into my Word 6 version (I'm currently at 970503). It'll take a
few days for me to complete, and I'll post here again when I've uploaded
my new version to my web page. The URL will remain the same, so just
follow Paul's link.

Phil

PS. The next thing I may look at is a script to convert the whole
document into neatly formatted HTML (although I'm not planning to have
any hyperlinks). Don't hold your breath...

--
\|/ ____ \|/   int c,a,x,y;main(){for(;a<2000;c    Phil Carmody,

/_( \_ / )_\   x=a%80-40,y=a/80-13,c+=(x=400-x*    Scientific Generics,
   \__U_/      x-y*y*4)>0?x:0,a++%80?c/80:6]);}    Cambridge, UK



Sat, 15 Jan 2000 03:00:00 GMT  
 Unconditional jump penalty on Pentium

Quote:

>I know that a branch misprediction costs at least 5 cycles on Pentium. How
>about an unconditional jump? Does it incur any penalty at all? Is there any
>difference in a short unconditional jump vs. a long unconditional jump?
>Thanks a lot.

The penalty for mispredicting an unconditional jump is 3 clocks on Pentium,
4 on PentiumMMX, much more on PPro and PII.  Misprediction occurs if the jump
is not in the branch target buffer.  Indirect jumps and returns can of course
be mispredicted too.

You will find all details on my homepage


Agner Fog, Ph.D.                            Pentium optimation manual at
Denmark                                     http://announce.com/agner/assem



Mon, 17 Jan 2000 03:00:00 GMT  
 
 [ 4 post ] 

 Relevant Pages 

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5. Pentium 3 vs Pentium 4 benchmarks

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7. Pentium & Pentium II specs

8. Pentium & Pentium II spec

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