|Probably the PC2700 if your motherboard supports it. |
You need to let us know what your motherboard is; exact model number. Or, if this is a manufactured system like a Dell, hp, etc. the exact model number of the machine.
Why? Because no Athlon XP runs at 1100Mhz. Several use a 11x multiplier though. I suspect your motherboard is set up wrong for the processor you have installed.
Try SIW from
to identify what's installed.