You can't just buy a PPC and fit it to a CS Mk 3 to make a CSPPC.
First of all, the PPC chip used on CSPPC cards is a
BGA or "Ball Grid Array" type, which can't be attached without specialist equipment and knowledge. So unless you know someone with a reflow oven, or a proper infrared heater, you're stuck at the first obstacle.
Even supposing you had the required ability and skill to successfully retrofit a BGA CPU to an already populated board, the card itself still wouldn't function as a CSPPC. All the glue logic, and power regulation parts required by the PPC are not attached to Mk3 cards. It was simply not worth the extra money for Phase 5 to pay for parts that have no use on the Mk3.
Really, it just won't work.
