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1.8 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 3.3 VSB applied.
NOTE
If the battery and AC power fail, custom defaults, if previously saved, will be loaded
into CMOS RAM at power-on.
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 12 shows the location of the battery.
1.9 Legacy I/O Controller
The I/O controller provides the following features:
• One serial port header
• Serial IRQ interface compatible with serialized IRQ support for PCI systems
• PS/2-style mouse and keyboard interfaces
• Interface for one 1.44 MB or 2.88 MB diskette drive
• Intelligent power management, including a programmable wake-up event interface
• PCI power management support
The BIOS Setup program provides configuration options for the I/O controller.
1.9.1 Serial Port Interface
The serial port header is located on the component side of the board. The serial port
supports data transfers at speeds up to 115.2 kbits/sec with BIOS support.
For information about Refer to
The location of the serial port header Figure 10, page 42
The serial port header signal mapping Table 13, page 44
1.9.2 Diskette Drive Interface
The I/O controller supports one diskette drive. Use the BIOS Setup program to
configure the diskette drive interface.
For information about Refer to
The location of the diskette drive connector Figure 10, page 42