While uname -a can give you some useful information about the system that you are running you might still need more detailed information about what type of CPU you are running.
bash-2.03$ uname -a
SunOS server-1 5.8 Generic_117350-24 sun4u sparc SUNW,Sun-Fire-480R
bash-2.03$ isainfo
sparcv9 sparc-bash-3.00$ uname -a
SunOS server-two5.10 Generic_125101-10 i86pc i386 i86pc
-bash-3.00$ isainfo
amd64 i386