Pls. what does this 4 and 8 phase PWM do
The PWM or Pulse Width Modulator, regulates power to the cpu. The trend has been to go from analog PWM's to digital PWM's.

Older P35 boards, like the ABIT IP35, used an analog 4 phase PWM that could power the Q6600 quads very well. The higher end boards switched over to 6 or 8 phase PWM's. The "budget" boards, like the DK boards use 4 phase PWM's. The Blood Iron (DFI's P35 budget board) had a 4 phase PWM that did not seem to do well at all with quads. However, DFI's subsequent DK boards, even though they use 4 phase PWM, seemed to do ok with quads. DFI seems to have implemented a better (more durable) 4 phase PWM in these boards.

However, an 8 phase PWM will run comparatively cooler and supply stable power more efficiently than a 4 phase PWM.

That's how I understand it.