Check out the information update pdf on the 2950's online manuals page (http://support.dell.com/support/edocs/systems/pe2950/en/index.htm). It has info about more updates than just the processors.

Thanks for that, I have already searched through the documentation and the only thing I can seem to find is :

If the front of your system chassis is labeled with a "II," your system is upgradeable to the Quad-Core
Intel® Xeon® Processor 5300 series

Which presumably means the 1st generation did not take 5300 series Quad core CPUs (only 5000 +5100 series) ??

The first generation motherboards only supported the Dempsey and Woodcrest procs which are only dual core.