x86_64 mail servers

[Mark Nienberg]

Matt Kettler wrote:
> Mark Nienberg wrote:
>> I've seen comments on this list that the x86_64 didn't seem to make much
>> difference and I admit it is simpler to use the plain x86 version, but
>> it bothers me a little to intentionally not use the software that is
>> specifically configured for the chip.
> 
> Why does it bother you?
> 
> Theoretically x86-64 should be slightly slower for most uses unless you:
> 
> 1) have a process that needs > 4gb of virtual address space
> 	-or-
> 2) does a lot of 64 bit math that can't be performed with SSE
> 
> The ability to have huge processes and large amounts of physical ram is the
> primary benefit of using a 64 bit computing architecture. The drawback is that
> pointers become larger, taking up more memory, and causing more memory I/O than
> would be needed if the app was 32bit. Unless you're actually using the larger
> memory space you're increasing overhead without any benefit whatsoever. Very few
> apps have such large memory footprints outside the realm of scientific
> simulation or massive database crunching.
> 
> 
> The other benefit of a 64bit computing architecture is the ability to do 64 bit
> math operations in one instruction instead of a series of 32 bit operations.
> However, very few applications regularly have any use for 64 bit operations
> outside of crypto, some games, and high-end engineering/physics. Even these
> regularly get their needs filled by using SSE, so the 64-bit math benefit is
> very limited.
> 
> There's some benefit here to apps using 64-bit file offsets or 64 bit time
> format, but I've never seen a "regular" application where either kind of
> calculation was performed often enough to have a noticeable impact on
> performance. Some scientific simulations may do a lot of 64bit time
> calculations, but most of those could readily use SSE for it.
> 

So I can take the easy way out and not feel guilty about it?  Fantastic!

Thanks for your explanation.

Mark Nienberg