4. Reset
40
Keyboard CTRL-ALT-DEL
Simultaneously pressing these keys calls a BIOS function that reboots the system. This method
does not work under operating systems that trap calls to this BIOS function.
Watchdog Timer (System Register Address 79h)
The watchdog timer may be programmed to generate a "CPU Init" if it is not strobed within a
given time-out period. This function is discussed in Chapter 7, "
Watchdog Timer
."
Backend Power Down Sources
Board Extraction
When a board is extracted from an enclosure (specifically, when the "board-select" pin is
disengaged), the hot swap controller unconditionally removes backend power from the board
and holds the board in reset.
Low Voltage
When any of the 3.3V, 5V, or 12V supply voltages are detected to be below an acceptable
operating limit, the hot swap controller unconditionally removes backend power and holds the
board in reset.
Overcurrent Fault
If a power fault condition (overcurrent) is detected, the hot swap controller removes backend
power and turns the Health LED amber. The board is held in reset.
NMI Sources
Watchdog Timer (System Register Address 79h)
The watchdog timer may be programmed to generate a non-maskable interrupt if it is not
strobed within a given time-out period. This function is discussed in Chapter 7, "
Watchdog
Timer
."
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