1MB or 2MB L2 Cache Memory (4045 and 4046) must be installed in pairs.

 Memory must be installed in pairs.  CPU memory and memory card must be of equal capacity. Because of space limitations caused by the regulator card and a large MCM on the new processor card, there is only one memory card slot.
      The memory MB on the processor card must equal the memory MB on the memory card.  There are 8 SIMM positions on both cards.Memory can be increased to 512MB by using 256MB Processor Card SIMM Memory and a 256MB Memory Card.  A number of new feature codes have been created to handle memory granularity.

7012-39H Memory Card (illustration HERE)
         S4.6         52G4801    4MB 70F9973 
         64MB/512MB              8MB 70F9976 
                                16MB 43G1796
                      88G3680   32MB 65G6452