Re: cpu comparison

From: ktm@rice.edu
Subject: Re: cpu comparison
Date: ,
Msg-id: 20110718231936.GA29080@staff-mud-56-27.rice.edu
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In response to: Re: cpu comparison  (Tomas Vondra)
List: pgsql-performance

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cpu comparison  ("M. D.", )
 Re: cpu comparison  ("", )
  Re: cpu comparison  (Tomas Vondra, )
   Re: cpu comparison  ("", )
   Re: cpu comparison  ("M. D.", )
    Re: cpu comparison  (Samuel Gendler, )
 Re: cpu comparison  (Josh Berkus, )
 Re: cpu comparison  (Greg Smith, )
  Re: cpu comparison  (Scott Marlowe, )

On Mon, Jul 18, 2011 at 11:56:40PM +0200, Tomas Vondra wrote:
> Dne 18.7.2011 22:11,  napsal(a):
> >> > In my testing I have a 32bit CentOS on the x3450, but a 64bit CentOS
> >> > on the E5335.  Can this make such a bit difference or should the
> >> > perform fairly close to the same speed?  Both servers have 8GB of
> >> > RAM, and the database I tested with is only 3.7GB.
> >> >
> >> > I'm a bit surprised as the x3450 has DDR3, while the E5335 has DDR2,
> >> > and of course because of the cycle speed difference alone I would
> >> > think the X3450 should beat the E5335.
> >> >
> > Yes, you have basically shown that  running two different tests give
> > different results -- or that an apple is not an orange. You need to
> > only vary 1 variable at a time for it to mean anything.
>
> He just run the same test on two different machines - I'm not sure
> what's wrong with it? Sure, it would be nice to compare 32bit to 32bit,
> but the OP probably can't do that and wonders if this is the cause. Why
> is that comparing apples and oranges?
>
It is only that 32 vs. 64 bit, compiler and other things can easily make
a factor of 2 change in the results. So it is not telling you much about
the processor differences, neccessarily.

Regards,
Ken


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