Here's a zoomed up image
With this info, we decided to push a 1.42GHz mini, that already had managed to run at 1.58GHz.
We took the R52 resistor off and bridged the other side, to reach the higher speeds. Of course, the better way of doing it would be to put the resistor back, but they are really small, and it works without them anyway.
We then put the machine back together, replacing the factory thermal pad by some Artic Silver 3.
Crossing our fingers, we switched the Mini on and we heard the comforting startup chime. Bingo !! Our Mac mini now flies at 1.67 GHz
The first few tests that we ran went smoothly, without any freezes. Michael told us his mini has been running at 1.73GHz for a while now, without any ill side effects.
Beware though, that the soldering involded is quite a pain in the ass...
Here's a recap of the resistors and the according frequencies :
0 means the resistor in in place, and 1 means no resistor. We also can now see the 1.33GHz frequency, unavailable with the previous hack.
We left the Mac mini running all night, crunching 16 millions fractals in Altivec Fractal Carbon (which is the maximum the program will let you run in one go) and the little dude is humming along this morning. If the current Mac mini can take a 250MHz overclock, it's pretty safe to say that they have some room left for upgrades.
Finally, Michael mentionned that the 1.25GHz mini has a different heatsink, which probably cannot withstand much more than what it was designed to.