lscpu

There are many GUI tools (like i-Nex) and commandline utilities in Linux to look up system information. To get information about the CPU, I like lscpu. The reason being that its name is the easiest among all tools to remember. It shows information about the CPU vendor, architecture and cache sizes.

If you find that this tool is not present on your system, just install the util-linux package:

$ sudo apt install util-linux

Tried with: Util-Linux 2.20.1 and Ubuntu 14.04