Card Cage

In the card cage (see Figure D-1), board slots are numbered from right to left: 1, 3, 5, 7, and 9.

This seemingly unconventional numbering system is derived from the slot numbering used in the general card cage design of the Enterprise server family. The Enterprise 3500 server card cage is based on the Enterprise 4500 card cage, which is double-sided, with even-numbered slots (0, 2, 4, 6) on the front and odd-numbered slots (1, 3, 5, 7) on the back. The Enterprise 3500 card cage uses the system internal SCSI bus (slot 1), which in turn dictated the use of the back half of the Enterprise 4500 card cage design

In most respects, all five board slots in the card cage are equivalent. However, slot 1 is the only slot that is physically connected in the card cage to the SCSI bus on the centerplane. Slot 1 is therefore normally reserved for an I/O+ board, since the CPU/Memory+ board does not have a SCSI bus controller.