[CentOS] cpu type

      I have a quick question.
      The board and CPU that I'm using in one of my machines was given
to me. I didn't take the time to look up the info on the board or
anything. I was busy, so I just put the board in a pc case, hooked
everything up, and loaded the os on the machine. 
      I didn't know it at the time, but there's a chance it may be a
64bit board and cpu. I don't want to pull the machine out of the desk,
and open it up to find out. Is there a command entered by way of the
terminal window that will tell me what kind of cpu I have? I want to say
that it's an AMD sempron 3000+, but I'm not sure. 

Thanks

Jim