Hardware Reference
In-Depth Information
Note that many newer systems have extended CMOS RAM with 2KB, 4KB, or more.
TheextraroomstoresthePlugandPlayinformationdetailingtheconfigurationofadapter
cards and other options in the system. As such, no 100%-compatible standard exists for
the way CMOS information is stored in all systems. You should consult the BIOS manu-
facturer for more information if you want the full details of how CMOS is stored because
the CMOS configuration and setup programs typically are part of the BIOS. This is an-
other example of how close the relationship is between the BIOS and the motherboard
hardware.
BackupprogramsandutilitiesareavailableinthepublicdomainforCMOSRAMinform-
ation, which can be useful for saving and later restoring a configuration. Unfortunately,
these programs are BIOS specific and function only on the BIOS for which they are de-
signed. As such, I don't usually rely on these programs because they are too motherboard
and BIOS specific and do not work on all my systems seamlessly.
Table 5.2
shows the values that might be stored by your system BIOS in a special CMOS
byte called the
diagnostic status byte
. By examining this location with a diagnostics pro-
gram, you can determine whether your system has set trouble codes, which indicate that a
problem previously has occurred.
Table 5.2 CMOS RAM Diagnostic Status Byte Codes
