It would seem that on the older cpus there were two on board pll circuits one for the core (VCCA) and one for the FSB (VCCIOPLL). On the C2D this would appear to have been reduced to a single input (VCCPLL).

Looking at the white papers for the core2duo and the Pentium D I have noticed a few things in regards to these voltage inputs:

  1. VCCA and VCCIOPLL pins are static across both packages
  2. The documented use of this pins is not noted for some reason on the c2d white sheet (perhaps because they have no use?)
  3. The VCCPLL pin (D23) is referenced as FC9 on the older cpus - and is documented as an output rather than input
  4. The VCCPLL is documented as the voltage supply for the FSB PLL (perhaps the need for the cpu pll supply voltage has gone?)


As such I think it's still prudent to keep the separate references up but I will include VCCPLL as a separate entity for current cpus