That's a rather unusual problem, but not unheard of.
Knowing which model of Asus mobo you are using might
Run Everest Home Edition from http://www.lavalys.com/product...ew.p...ang=en&pageid=1
Or, SiSoftware Sandra 2004 from http://www.sisoftware.co.uk/in...?dir...all&langx=en&a=
Either one will give you some information about which motherboard you really have installed in there.
Also, knowing exactly what it is running at, when it does boot at 638MHz, would definitely
Run WCPUID, or CrystalCPUID, (both are free programs), to get all the pertinent details about what CPU you actually have in there, and what speed it's currently running at...
Make a note of the L2 cache, the multiplier, and the Family - Model - Stepping ID...
From that info, we can figure out exactly what it is you have, and what it should be running at.
WCPUID is available from this page... http://www.h-oda.com/
CrystalCPUID is available on this page... http://crystalmark.info/?lang=en
Here is my new PCChips M848A' ">http://img.photobucket.com/alb...2_T-2-3-3-6-2_M848.jpg v2.1, with a 1700+ @ 2411 MHz, and my trusty old PCChips M810L' ">http://members.lycos.co.uk/mmm...00MHz_Sandra_tests.jpg v7.1A, with a Barton 2500+ @ over 3500+. Some of my fancy cars are on this pag