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From: Robert Watson <rwatson@FreeBSD.org>
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To: Mike Tancsa <mike@sentex.net>
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cc: freebsd-performance@freebsd.org
Subject: Re: 64bit CPUs
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On Sun, 1 May 2005, Mike Tancsa wrote:

> A somewhat obvious question to some perhaps, but what server application 
> mix on FreeBSD today sees an improvement using 64bit CPUs ?  In my ISP 
> centric world, my big apps are BIND, IMAP/POP3, httpd via apache, SMTP, 
> AV and SPAM scanning, and firewalls/routing.  Apart from larger RAM, why 
> would these benefit from the 64bit world ?  Or would they ?

RAM/address space is the big reason.  In fact, applications compiled for 
64-bits may well run slower than 32-bit ones running on the 64-bit kernel. 
Note that systems like Solaris default build many programs as 32-bit, 
since there's no benefit to running ls(1) with a 64-bit address space.

On the other hand, if you need a large memory system, running a 64-bit 
system will give you better support and utilization than a 32-bit system 
runing with PAE, at least on FreeBSD.

Robert N M Watson