@submix8c
Actually SP2 wrongly used NTOSKRNL where in athlon need NTKRNLPA so MS Fixed it on SP3.
What you actually mentioned above , many OEM Already added the fix in their Disc.
These are some weired problem faced by athlon user but since phenemon this problem gone.
This happened due to AMD64 Dualcore architecture was not detected by SP2 .
You mentioned why? AMD team was ahead of MS.
this is due to fact most people runs xp sp2 that time. i am guesing