Real-Time Clock, Cmos Sram, And Battery - Intel YA810E Technical Product Specification

Intel Desktop Board YA810E Technical Product Specification

1.6.4 Real-Time Clock, CMOS SRAM, and Battery

The real-time clock is compatible with DS1287 and MC146818 components. The clock provides a
time-of-day clock and a multicentury calendar with alarm features and century rollover. 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 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 3.3 V 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
SRAM at power on.
NOTE
The recommended method of accessing the date in systems with Intel
from the Real-Time Clock (RTC) via the BIOS. The BIOS on Intel desktop 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 Intel desktop boards
24
®
desktop boards is indirectly
Refer to
http://support.intel.com/support/year2000/