Vcore / Vdimm / VChipset mods.
Having just borrowed a P4 Extreme Edition, the only board that was available
for me to use it on was the Epox Canterwood. Since the board only offers up
to 1.6v for the Vcore with the latest bios, a Vcore mod was in place. Took me
quite a while to figure this out as the feed back pin doesn’t work since it
is directly grounded. Take note that these mods are done on the Rev 1.1
Here’s the Vcore regulator, the SC2643.
You will need to remove the 0 ohms resistor circled in the picture, and replace
it with a variable resistor. I use a 2.2k ohms VR. However TAKE NOTE that unlike
normal mods, bigger resistance here means higher voltage. So set your VR to
zero resistance first then tune up the resistance slowly to get higher Vcore.
There is a limit however and once passed this limit, more resistance will drop
the voltage instead. The max I could get from it is 1.88v. At least much better
than the 1.6v cap.
For Vdimm, here’s the Vdimm regulator, the SC2616. You need a 5K VR from pin
1 to ground, or just solder the VR to the solder pad in the above picture. Lower
resistance and you get higher voltage.
For the Northbridge voltage, contrary to people’s belief, it is not shared
with VAGP. Here’s where to measure it from, the mosfet leg shown.
Connect a 500K VR from pin 3 to pin 8. Set it to 500k ohms first. Lower resistance
to increase voltage.
I was able to hit 330 FSB with some help from these mods.