Hi I have an ageing Mac Pro A1289 (5.1). When stripped down to the motherboard and (bare) processor card the diagnostics are fine. When the (dual) processor card is populated with a single processor, the front panel light flashes and the startup fails. How do I find the cause of the issue? If this is due to a matched pair of processors not being fitted, how does the system know this on the basis of only one processor?