A7M266 and Athlon XP (Palomino)

Hello,

I have an A7M266 with a Thunderbird 800MHz
running fine since years.

Now I wanted to upgrade with an Athlon XP
1700+ (1466MHz) ARKGA (Palomino). Unfortunately
it doesnt work. Fans start to spin but nothing
else happens (no beeps, blank screen). The
Board runs in Jumperfree-Mode, Voltage Jumpers
set to default, FSB switched to 133MHz.
I tried the latest stable (1007) as well as the
latest beta (1008) BIOS but still no luck
With the TB800 everything is still fine.
Anyone a hint what to try before I consider
the cpu broken?

Thanks & greetings,
Leander