I knew there is a soft way to do so, but I really like to find out another way 
Now come with me, I'd like to share my experience with all you guys. 
This is hardware modification! You play this on your own risk!
The most headache is that the position of PLL IC is different from most others(such as IBM,HP), because it's on the backside of the mainboard. That is to say, you have to dismantle it completely. In my opinion, CPU is easy to be overclocked. The importance is whether your memoty module can support 33% overclock or not. In other words, your memory module will work on 333*1.3=443 MHz after overclocking if you use DDR 333 alone. So I mix a DDR266 and a DDR333, in this case all modules only need to work on 266 x 1.3=354 MHz. It plays a crucial role in the process of overclock.
shame... they put PLL IC on the backside
according to Pin Configuration of CY28346, let A (pin 55) & B connect with a 1k resistor so that A can get a High Potential (just like C & D)
I tested my D600, and it has worked stablely by now
LOL god damn, i855PM works on FSB 533MHz!
on full speed:
on 800MHz with speed step:
DDR status:
Super PI 1M calculation
Have fun, dell fans
Now come with me, I'd like to share my experience with all you guys. This is hardware modification! You play this on your own risk!
The most headache is that the position of PLL IC is different from most others(such as IBM,HP), because it's on the backside of the mainboard. That is to say, you have to dismantle it completely. In my opinion, CPU is easy to be overclocked. The importance is whether your memoty module can support 33% overclock or not. In other words, your memory module will work on 333*1.3=443 MHz after overclocking if you use DDR 333 alone. So I mix a DDR266 and a DDR333, in this case all modules only need to work on 266 x 1.3=354 MHz. It plays a crucial role in the process of overclock.
shame... they put PLL IC on the backside
according to Pin Configuration of CY28346, let A (pin 55) & B connect with a 1k resistor so that A can get a High Potential (just like C & D)
I tested my D600, and it has worked stablely by now
LOL god damn, i855PM works on FSB 533MHz!
on full speed:
on 800MHz with speed step:
DDR status:
Super PI 1M calculation
Have fun, dell fans
. I will give it a good stress test and then do the other one as well.
My DDR333 256+ DDR 333 512 works bad before. but DDR266 256+ DDR333 512 works fine! (RAM SPD do not has config which higher than 133/266MHZ ! CL 2.5_3_3_6 or 2.5_3_3_7 ) 
My Thermal heat pipe should broken(DELL's Problem). Fan wind did not so hot even CPU get 90C degree . So, I'm using RightMark CPU utility now. It's a good software!
??? CPU-Z states that with the 256 DDR266 and 1024 DDR333 in there that both sticks are running at DDR354 
Great mod though
