Variable Firefox performance between installed and not installed versions

[bowlofducks]

Does anyone know why there's such a large performance difference of Firefox between when I install Firefox, and when I just download it and run it in a folder on my desktop?

Example: http://bellard.org/jslinux/

That runs 20% faster when I just download and run Firefox from a folder, compared to the installed version.

I've also run the performance test here http://www.webkit.org/perf/sunspider/sunspider.html

Firefox runs up to 50% faster or slower on certain tests when comparing the results of installed and not installed Firefox. Overall on that test speed is around the same on average, because some parts of the test it'll be 10,20,50% faster, and other parts 10,20,50% slower. I've tried this with Firefox 6 and 7. The variability of results occurs between both versions.

[raja.genupula]

many reasons , you can solve them by using this
http://kb.mozillazine.org/Standard_diagnostic_%28Firefox%29

[lovinglinux]

Are you comparing the same version of Firefox?

[raja.genupula]

actually i havent remembered that what kind of problem we are going to have . but what ever he is saying is true . i read one post in our forums thats saying as firefox after some days of usage , its going to get slow ,but chrome didnt have that . as this i have read . he is comparing same version but in performance consideration at the time of a fresh install & after using of some days .