Performance on 64 bit Linux vs 32 Bit

[ram]

On Tue, 2007-10-23 at 10:15 +0100, Randal, Phil wrote:
> We're running it fine here on 64-bit CentOS 5.
> 
> Dell 2950, 4GB RAM, quad-core Xeon, mirrored hard disks.
> 
> Using a 64-bit build of McAfee's uvscan along with ClamAV.
> 
> Cheers,
> 
> Phil
> 

On 32-bit Centos 4.4 ( 4GB Ram , 2 x dual core Xeons )
We get upto 20-35k mails hitting the server per hour 


We run caching DNS and rbldns zones for most "rsyncable" DNS lists for
SA ( spamhaus , dsbl , dnswl , sorbs surbl etc ) 
Most connections , around 85% , get rejected by RBL checks at postfix. 

The rest of the mails get scanned with nearly 3-5 minutes delay. Though
sometimes it oddly takes longer 

Can this be improved by upgrade to 64-bit. This is what I am looking
for 

Thanks
Ram