To guarantee compatibility with non-PAE processors, the 32-bit versions of Linux Mint Debian come with a 486 kernel by default. This kernel does not support SMP, and as a consequence is only able to detect one core and one CPU. If your CPU has multiple cores, or if you have more than one CPU, simply install the 686-PAE kernel and reboot your computer.
About Linux Mint
Linux Mint is an Ubuntu-based distribution whose goal is to provide a more complete out-of-the-box experience by including browser plugins, media codecs, support for DVD playback, Java and other components. It also adds a custom desktop and menus, several unique configuration tools, and a web-based package installation interface. Linux Mint is compatible with Ubuntu software repositories.