[GigaFrog]

You mean this is where we post our mods?

OK, I soldered ceramic capacitors in the back of the CPU socket. When I measured the Vcore with a 400MHz oscilloscope, it was so noisy that I decided to add high frequency capacitors. They are chip surface mount (size 0603) that fit in between Vcc and Vss pins. I alternated with a 100pF, a 10nF, a 100pF, ... a total of about 50 capacitors soldered in between the FCPGA470 socket pins. I got the pinout from the CPU datasheet.

Just these ceramic caps allowed me to increase the CPU freq from 1035MHz to 1050MHz. The reduction of noise decreased the stress on the processor (by reducing overshoots).
Still, the 400MHz scope was abble to trigger between 1.95V and 2.23V, on a Vcore set at 2.05V. Unfortunately, I didn't write down the trigger levels before adding the caps, but it was probably uggly.

Considering overshoots, they were pretty high too at the leads of the electrolytic caps, so I added a 100pF and a 10nF ceramic cap between the leads of each electrolytics. Because the ceramics can handle 50V, they will absorb high freq overshoots before they even reach the electrolytics and damage them (they are rated at 6.3V). One of the first reason of failure of a motherboard is the death of electrolytic caps (they go short when they die, resulting in heavy damage to the Vcore regulation circuitry).

My Vcore is still fluctuating by 0.11V between iddle and load, and my next mod is to dynamically switch the VID pins to stabilize the Vcore. I am almost done with the circuitry that will do that, will post results.

I made all these mods at work, under binocular, with a fine tip temperature regulated soldering station. Not the kind of stuff to attempt with a 50W standard soldering iron.