Pros and Cons of amd64 (versus i386).

[Pete French]

> If your running a desktop, I'd recommend sticking with 32-bit.  For a  
> server doing a lot of I/O, go with 64-bit.  The Athlon will run very  
> fast in both modes, but your software compatibility is better in i386  
> mode.

Interesting comment - I have a server at home with a pair of Opteron 242s
in it that I just built and was wondering about switching to amd64 mode.
It's primary purpose is to provide file servring over Samba, mail
using imapd (large mbox format files) and also to be a firewall
using PF/ALTQ. So it's pretty much entirely doing I/O.

I was thinking of moving this to amd64, but was kind of put off by results
from a test system I setup using an Athlon 64 3700+ to talk to this
machine. The opteron box is currently running 6.1-PRE/i386, and the 3700 is
runiing either Windows XP or 61-PRE/amd64. Under Windows I can completely
saturate the ether comming in, and get 70% bandwidth going out (it's gig
ether). Under amd64 on the client end I can only get about 55% utilisation
in both directions. This surprised me a lot as when I was running i386
on that box it was always faster. Of course a number of variables have
changed since then (primarily moving from a broadcom gigabit card to using
the onboard realtek card), but I was concened that the difference was due to
the 64 bit operating system, as opposed to superior windws drivers, which
seemed unlikely!

I know that what I should do is install i386 on the client and test again, but
doing that will lose my only 64 bit environment so I am loathe to do so. Any
comments ?

-pcf.