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1.13 Real-Time Clock Subsystem
A coin-cell battery (CR2032) powers the real-time clock and CMOS memory. When
the computer is not plugged into a wall socket, the battery has an estimated life of
three years. When the computer is plugged in, the standby current from the power
supply extends the life of the battery.
The clock is accurate to ± 13 minutes/year at 25 ºC with power applied through the
power supply 5V STBY rail.
NOTE
If the battery and AC power fail, date and time values will be reset and the user will be
notified during POST.
When the voltage drops below a certain level, the BIOS Setup program settings stored
in CMOS RAM (for example, the date and time) might not be accurate. Replace the
battery with an equivalent one. Figure 1 on page 13 shows the location of the battery.
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