I have a very noob question but I would like to know how to choose the CPU for server.
I need to build a server which its data could be accessed by 100+ computers at the same time. And the data could be like a few hundred MB in size.
Should I get a CPU with more cores or more cache or other spec?
It's not a noob question depending of your scenario, and I'm afraid if you can't find the answer you should find someone who does, and it won't be in a public forum, better to pay for a good consultant than screw it up. He'll ask for things like like your network topology, how this data is accessed, what applications need to run on this server, how much redundancy and availability you need and how heavy every data request is on the system, and depending on these answers the CPU you'll pick is your smallest worries, as high speed storage and huge amounts of memory can be expensive.
Get someone who can work in delimitating this scenario for you and he'll have the answer of the hardware you need. You'll recoup the money somehow, the odds of you finding someone on an annonymous forum that will give you a solution that won't cost more money in the future are really small, and you don't have to be that penny-wise-pound-foolish.