Win 98SE with a ECS KT-600A MB & AMD XP1800 Mobile CPU

[usafdon 0]

I'm operating WIN 98SE with an ECS KT-600A Motherboard & AMD XP1800 Mobile CPU (266FSB)(AMD Part # AXMH1800FHQ3)..512 MB DDR PC3200 @ 400MHZ, 80GB Seagate HD. At 266 FSB MB Jumper settings, CPU operates at 800MHZ. At 333 FSB MB Jumper settings, CPU operates at 1GHZ. At 400 MHZ FSB MB Jumper setting, CPU operates at 1.2 GHZ. The CPU is rated at 1.53GHZ at 266 FSB. Why the heck is my MB running the CPU at 800 MHZ when I have the 266 MHZ FSB MB jumpers selected? I am running the CPU at 400 MHZ FSB MB Jumper setting now and the CPU is very stable, and runs at 30c (No Load) and 34c (Load). I envisioned this CPU to run at 1.53 MHZ at 266 FSB when I bought it..but can't get it there or overclock it beyond that. Can anyone help?...Thanks...Don.