When I got the Predator, it had 4 (dual) IP7 CPU boards installed. It turned the first cpu on the first board was faulty. This one vital when booting the system. The I discovered that between the 4 CPU boards, two have PROM chips labeled 070-0401-007 and 070-0400-007, and the other two have PROM chips labeled 070-0401-009 and 070-0400-009. The first is PROM version 3.3, the latter is 4.0.1 All IP7's are the same board revision (part#).

All boards must have the same PROM revision or they don't work together

I had one more faulty CPU in another IP7. In the end I mixed and matched untill I had 2 IP7 boards with the 4.01 PROM chips and 4 working CPU's, and 1 board with the 3.0 PROM revision and 2 working CPU's. Below, the quad CPU config is running, the third CPU board is standing by the side, and the two dead CPU's (actually, SM7 daughtercards) are on the deskside.