Run Intel processor diagnostic tool. If it's turbo boost related then it's either a bad motherboard or bad CPU. Nothing else can really have a direct relationship with boost behavior. Bent pins, standoff under motherboard in the wrong spot, bad CPU, just plain bad motherboard, bad BIOS firmware or BIOS ROM, faulty chipset driver installation. These are all things you've already looked at I think, so I'd run the diagnostic tool and see what it says.