Consolebus; Clocks; Reset Logic - Sun Microsystems Enterprise 6500 Reference Manual

6.2.1

ConsoleBus

The ConsoleBus provides system boards access to global system control and status
as well as to the keyboard, mouse, and serial ports. In addition, there is a NVRAM/
TOD chip that maintains the date and time and 8 Kbytes worth of data when the
power to the system is shut off.
The state of physical hardware conditions is maintained in registers on the clock+
board. Each of these registers has inputs generated from other subsystems on the
clock+ board, from other boards, or from the power supplies in the system. Some
clock+ board registers are reserved for controlling various states of the machine.
The ConsoleBus also provides a serial port interface and a keyboard/mouse
interface. The primary purpose of the serial port interface is to provide POST
messages during power-on. The serial port can be used as a console for systems
without a keyboard and display, and for standard serial peripheral hook-ups such as
modems and printers.
6.2.2

Clocks

The clock subsystem generates the clocks for the entire system. The base clock is
synthesized, then divided into various frequencies. The base clocks are then
"fanned-out" and driven to the centerplane by an array of driver chips. Two
processor clocks and one system clock go to each board slot on the centerplane.
6.2.3

Reset logic

The reset logic consists of four subcircuits for controlling the system reset and error
state:
Manual reset
System reset
XIR
System error
6-4 Sun Enterprise 6500/5500/4500 Systems Reference Manual • April 1998