lets take a closer look what are we doing:

I've read the Intel's Core 2 Duo/Quad processor documentation to figure out what are those pins.

On page 49 of Core 2 Duo processor, we can see that we are making a simple jumper between G30 (BSEL2) <-> J30 (VCC)





On page 60, G30 means:
BSEL2 - POWER/OTHER -> Output


And on page 61, J30 means:
VCC - POWER/OTHER -> ?



So, on page 75, I've found that VCC is an Input:



And on page 69, we can se an explanation what is BSEL[2:0]


and it points to Table 17 (page 30) which is:

I can't see a possible combination to 333MHz, just 266MHz (Q/X/E6XXX) or 200MHz (E4XXX). Maybe just newer processors have it (?)


So, this mod is simply make a jumper between BSEL2, an output FSB frequency selector, and VCC which is a simple power pin.