Intel ® 82802Ab 4 Mbit Firmware Hub (Fwh) - Intel D815EEA Technical Product Specification

1.6.2.3 Real-Time Clock, CMOS SRAM, and Battery
The real-time clock provides a time-of-day clock and a multicentury calendar with alarm features.
The real-time clock supports 256 bytes of battery-backed CMOS SRAM in two banks that are
reserved for BIOS use.
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.
The time, date, and CMOS values can be specified in the BIOS Setup program. The CMOS values
can be returned to their defaults by using the BIOS Setup program.
NOTE
If the battery and AC power fail, standard defaults, not custom defaults, will be loaded into CMOS
RAM at power-on.
NOTE
The recommended method of accessing the date in systems with D815EEA boards is indirectly
from the Real-Time Clock (RTC) via the BIOS. The BIOS on D815EEA boards contains a century
checking and maintenance feature. This feature checks the two least significant digits of the year
stored in the RTC during each BIOS request (INT 1Ah) to read the date and, if less than 80 (i.e.,
1980 is the first year supported by the PC), updates the century byte to 20. This feature enables
operating systems and applications using the BIOS date/time services to reliably manipulate the
year as a four-digit value.
For information about
Proper date access in systems with D815EEA boards
®
1.6.3 Intel 82802AB 4 Mbit Firmware Hub (FWH)
The FWH provides the following:
•
System BIOS
•
System security and manageability logic that enables protection for storing and updating of
platform information
Product Description
Refer to
Section 1.2, page 16
25