On 2/2/07, Dmitriy Kropivnitskiy <nigde@xxxxxxxxxxxx> wrote:
James Wilkinson wrote: > It's usually a bit faster. Just to avoid the confusion, are you saying that 64-bit capable processors are faster than 32-bit only or that application compiled for 64-bit architecture is faster then the same application compiled under 32-bit architecture on the same hardware. The reply to your post tells
He probably means that a 64-bit processor is "usually a bit faster" when running in 64-bit mode (that is, running a 64-bit OS) than in 32-bit mode.
me that people think you mean the former, where I was talking about the latter. I will not dispute the claim that 64-bit CPUs are faster then 32-bit, cause I don't think they make 32-bit only CPUs anymore (at least in the x86 architecture). So any 32-bit CPU will be just plain outdated and therefore slower then any modern 64-bit (and 32-bit capable) CPU. As
The issue at hand is that you think running a 64-bit OS brings little or no advantage over a 32-bit OS on a 64-bit processor unless you have a lot of RAM or need a large address space. Oh, and you do know it is possible to address more than 4 GB of RAM on a 32-bit processor with a 32-bit OS, right? Look up PAE: http://en.wikipedia.org/wiki/Physical_Address_Extension
for the applications, I believe the difference should be negligible unless the application is trying to use a lot of RAM. I think I have seen some benchmarks confirming this, but at the moment I cannot seem to find them.
There is a whole lot more to x86_64 than just addressing more RAM or having a larger address space. One of the biggest improvements is the fact that it has twice as many general purpose registers (x86 has 8, x86_64 has 16). Whether or not an application will perform significantly better in a 64-bit or 32-bit environment depends on the application and what it is doing exactly. The performance gains can be significant, even if you do not have a large amount of RAM. I run x86_64 Fedora because I bought a 64-bit CPU and want to take full advantage of my processor. Not that this discussion is helping the OP at all... Jonathan
