Recently i got AMD64 3000+. While i was looking for a Linux distro to install on it, i could not find the 64 bit version of the one i wanted to (Auditor)to be precise. Now i have installed Auditor.. though i am aware of the fact that i may not get the performance i should be expecting from a 64 bit processor/OS.
Now my question is.. what exactily is a 64 bit OS? Is it totally different code as to what is writted for 32 bit processors? Or is it the usual code being compiled on a 64 bit machine that makes the difference?
my next query would be.. would it improve the performance of my machine if i recompile the kernel (for Auditor) on the new machine? Following this, i would have a kernel compiled on a 64bit processor but, other applications still would be 32 bit ones. So does this make my system a true 64 bit OS?

A 64-bit OS is one which does exactly what you'd expect... takes full advantage of the 64-bit processor.
So in essence, some of the code is very similar (if not the same), but some of it will be different to cater for 64-bit capabilities and optimizations.

You will probably notice a large difference if you recompile the kernel on the new machine, since it will find and enable 64-bit support.

If you have a 64-bit kernel, you may find that some programs refuse to run if they were compiled for 32-bit; otherwise they will run in native 32-bit mode - in other words ignore the fact it's 64-bit, so you'll get no advantage.

Sam

More precisely, 64 bit vs 32 bit refers to the size of the various arguments that most machine code instructions for the microprocessor can handle. It also refers to the size of each of the microprocessor's internal registers. My understanding is that the source code for 64 bit is substantially the same as for 32 bit. It is the compiler that is different in that it will now produce 64 bit machine code.

well then.. what is the result going to be like in this scenario?

I have a precompiled 32bit Linux distro. I recompile the kernel with the gcc compiler that was already present in the distro (i.e. 32 bit). The kernel would now be compiled enabling the 64 bit flags.. so essentially the kernel should be 64bit.. right?

Something i found in kernel.org that i could not interpret fully..
can anyone explain what this means in "relatively" layman terms?
Do we need a 64bit gcc compiler?

Thanks.