The motherboard's BIOS (MSI, nvidia 560 chipset) has a setting related to PCI-e : it asks the PCI-e frequency, there is no "auto" - you need to enter a number between 100 and 150, therefore I have left this alone to 100 - the BIOS somehow must be able to set it independendly of anything else that's going on.
With everything at stock, raising the FSB stops working at 216MHz. Lowering *everything* I can (RAM, HT, CPU multiplier) allows me to reach 230MHz on the FSB before it will not boot any more. At that stage do I need to increase power to the CPU even though it is working at a low multiplier?