Hi Stefano,
I do not see any image inside your last post.
From the microchip doc :
The external quartz you can use with a PIC32 chip must be within the [3.5 40]MHz range.
If you use an External Clock, it must be within the [0 72]Mhz range.
You can use PLL multiplier to speed up internally the clock.
I do not know that is the max speed that can be obtained with a PIC32. It is probably not 1080MIPS (that is 1 Ghz : too fast !)
I attach a very simple example running the PIC32 starter kit. The PIC32 starter kit has an external Quartz of 8Mhz. In the example, I use PLL and get a 1 Mips speed. However, I could get a wide range of speed by modifying the
Desired Instruction Per Seconds.
All peripheral are not yet supported on the PIC32 family.