int x86_cpuid_string (char *buf, 
                      int max)

Place a string representation of the CPU in the string buf to a maximum of max characters. The general format of the string is:

manufacturer part Ffamily Mmodel Sstepping

This information is determined using the cpuid instruction. If it's not supported, then a subset (typically only the part) will be placed in the buffer (e.g. 486).