Can the IPB 3.0 be installed on a 64 bit Linux server or is better on a more classic 32 bit server?

The processor architecture doesn't play a major direct role with IPB3 - you should be researching whether your web server supports and takes advantage of the technology.

I am switching my server for a new one. To use more than 4Gb of RAM on a Linux Red Hut I can use on a 32 bit server with a HUGEMEM kernel or a Linux Red Hut 64 bit

I run IP.Board 3.0 on a 64bit CentOS install. As long as your OS and modules are 64bit, it's all good.

Doesn't 64 bit allow an enormous size of mySQL databases? Thats the only major difference I know of.

64 bit processors have a much higher integer limit. This allows for "bigger everything" in theory.

What you think is best? Shall I take a 32bit or a 64bit linux Red Hut server?

Personally, I would never use a 32 bit server OS anymore.

In terms of servers, there is no advantage to using 32-bit over 64-bit, and more than a few advantages to 64-bit.

i would agree, 32bit is so "yester-decade" ive been using 64-bit on my desktop since vista came out, (very well i might add!) as well as my old dedi and my current "cloud" VDS being 64bit, both of those had/have been wonderful! i see no reason not to use it..

afterall. you have only what? like 20 more years before 32bit cant count time any longer? xD

link okay, so 29 years.. but still..

Yeah my Vista Ultimate is 64 bit too because I have 8 GB of RAM on my system. It just removes a lot of limitations and, as Brandon said, allows for bigger everything. Remember, on x86 32 bit architecture, any memory over 3.5 GB is non usable (even with patches and updates). 64 bit is the way of the future, so I would recommend upgrading to 64 bit for sure.

Ultimately, IPB really doesn't care what processor architecture you use. ;)