IEI Integration ICE-DB-9S - Manual (Page 136)

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ICE Module
Figure 6-23: BIOS Main Menu – Updated BIOS Version (MR11)
A.1 RTC Overview
A Real-time clock (RTC) is a basic hardware device that keeps track of the current
time of the computer. A RTC can be built in a chip or embedded in the system. When
the computer is turned off, the battery on the motherboard provides power to the RTC
to keep track of the current time. The RTC is usually used in personal computers and
embedded systems.
A.1.1 How to Calculate the Battery Life
The RTC requires an external battery connection to maintain functionality and its RAM
while the south bridge is not powered by the system.
The battery life can be calculated by dividing the capacity by the average current
required. For example, if the battery storage capacity is 170 mAh(assumed
usable)and the average current required is 6 μA, the battery life will be at least:
170,000μAh / 6 μA=28,333 h=3.2 years
The voltage oh the battery can affect the RTC accuracy. In general, when the battery
voltage decays, the RTC accuracy also decreases.