Which -march/tune flags for Xeon processor?

Hi,

I have a dual Intel Xeon workstation which I want to tune for GCC.
What -march and -mtune flags should I call GCC with to optimize performance? None of the simpleton options that I recognize (pentium2, pentium3, etc.) appear to recognize the chip's "Xeon" nature.
So here's is the /proc/cpuinfo and any help would be appreciated.

Thanks,
Charlie

zender@soot:~/nco/bld$ more /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Xeon(TM) CPU 2.80GHz
stepping        : 7
cpu MHz         : 2791.996
cache size      : 512 KB
physical id     : 0
siblings        : 2
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush d
ts acpi mmx fxsr sse sse2 ss ht tm pbe cid
bogomips        : 5521.40

processor : 1
vendor_id : GenuineIntel
cpu family : 15
model : 2
model name : Intel(R) Xeon(TM) CPU 2.80GHz
stepping : 7
cpu MHz : 2791.996
cache size : 512 KB
physical id : 0

Charlie Zender, [email protected], Department of Earth System Science
University of California, Irvine CA 92697-3100. Tel: (949) 824-2987