it depends on which version of CPU you have
The original CPU require C1,C2<C4 or C8 (and was not zipped)
CPU V requires P0
CPU x requires PX
at least that is the way I remember things, it has been a number of years since I have had to do this so could be wrong.
A Maintenance contract is essential, not a Luxury.
Do things on the cheap & it will cost you dear