Linux 2.4.33 on Dell Workstation

I'm using a Dell workstation with 2x2.8GHz Intel Xeon (old generation,
based on P4 I suppose...) and 3GB RAM.
I've seen in the kernel configuration that the cpu is set to 486!
If I want to recompile, how to set cpu in the kernel and memory for max
performance with my workstation?
Many thanks