On Wed, Oct 10, 2007 at 09:24:25AM -0500, Robert C Wittig wrote:
| Siju George wrote:
| >I thought by running an amd64 kernel will get me twice the speed than
| >an i386 on an amd64 machine since one is 64 bit processing and the
| >other is just 32 bit :-(
| >
| 64 bit processors (combined with 64 bit capable operating systems) have
| the ability to address more RAM than 32 bit processors because 64^2 is a
| much larger number than 32^2... lots more RAM addresses).
| This does not speed things up, though, until you run out of RAM, and
| start having to access the swapfile.
| The processor's speed... MHz, GHz, etc., will determine how fast the
| processor itself can process instructions.

Depending on your software, 64 bit processors can be quite a bit
faster. If you're dealing with 64bit integers, using 64bit registers,
etc., a lower clocked 64bit CPU might be faster than a 32bit CPU
clocking at a higher rate. In short: There is no short answer. It
depends on what you're doing.

>From what Henning tells us (and what sounds logical to me), grabbing a
ethernet frame from a NIC and putting it on another NIC doesn't really
change much from 32bit to 64bit.

Your compiler also comes into play. If that is more tuned towards a
certain 32bit architecture (such as i386) than a certain 64bit arch
(because it's less populair, such as sparc64 or hppa64 or mips64),
this will impact your performance quite a bit.


Paul 'WEiRD' de Weerd


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