If the processor is not compatible, it means the motherboard is not validated for the power and thermal specifications of the processor. It also means that the BIOS has no explicit support for the stepping and frequency of the processor.
Since the motherboard and processor are not designed to work together, what you can expect is an unstable system at any time and you can expect it to fail sooner than expected and this can be caused by anything, such as a simple BIOS update on your board, or it can even just happen.
Instability issues cover basically everything: from data faults up to boot issues.
This automatically voids the warranty of both server board and processor since, the 3 year limited Warranty only covers manufacturing defects while, usage not in accordance with product instructions, misuse, neglect, alteration, repair, improper installation, improper testing is not covered:http://download.intel.com/support/processors/sb/english_3yr_warranty.pdf
Hi,
ok, thx - so nothing definitve but as expected a lot of maybe's 
rgds,
Thomas
