Optiplex 745 BIOS Modification

Hi,
I've been reflecting on some of my prior posts and it dawned on me that there are CPUs that the 745 - I own the MT - is physically capable of running but can't due to the BIOS. That seems like such a shame as it limits the lifespan of the machine. In my view this is merely the result of Dell enforcing a cut-off pint for their newer range of PCs - I'm not disparaging them with that remark, it's perfectly understandable from a business perspective. However, I was wondering if it's possible to modify the BIOS? Has anyone thought of doing this, and if so, is there a functional custom BIOS out there?