AT&T 3B2/300 Technical Reference Manual page 415

FUNCTIONAL D E S C R I P T I O N - - - - - - - - - - - - - - - - - - - - - - - - - -
CM520A Backplane Board
The CM520A is a 12-slot backplane board. The system board plugs into the bottom of the
backplane board. There are 7 1/0 slots to hold a maximum of either 3 double-wide or 7 single-width
feature cards. There are 5 performance slots consisting of 2 memory, 2 buffered microbus (for MPE
cards), and 1 VCACHE connectors. Figure 3-52 shows the functional diagram of the CM520A
Backplane. Exact signal and pinout information is provided in Appendix B.
Power and ground (+5 volt, +12 volt, -12 volt, and GRD) for the features cards are supplied from
the power supply via connectors on the backplane. The floppy disk drive is connected directly to the
backplane via a 34-pin connector. The "Power" and "Diagnostic" LEDs and NVRAM battery are also
connected to the backplane.
3-162 TECHNICAL REFERENCE MANUAL