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Last Update: November 8, 1999.

BIOS and Real-time Clock Management

This page covers the following topics -

  1. BIOS (Basic Input-Output System) Explanation
  2. Real Time Clock (RTC) Discussion
  3. Software for Diagnosing and Repairing Updated

BIOS (Basic Input-Output System) Explnation

The BIOS (Basic Input Output System) is a hardware interface program between the basic computer hardware and the operating system that provides a standardized interface between the operating system and the hardware.

One of these standard interfaces is between the Real Time Clock in the hardware and the operating system. In general, most of the Real Time Clock hardware made before 1995 did not allow for a year greater than 1999; thus the "Y2K Problem."

A second level of confusion in this area is the fact that most operating systems request the date from the Real Time Clock only upon startup; they maintain an independent copy in parallel to the hardware while the system is running. And then the next system restart goes back to read the hardware value. As such, tests that set the operating system time to a few minutes before the end of the century and then get a readout a few minutes later do not test the entire hardware. It is necessary to set the operating system date and time to 23:57 on December 31, 1999 and then turn the power off for a few minutes. If the system time is not correct, it is probably desirable to upgrade the BIOS.

A simple test will probably verify that you have a Y2K compliant BIOS:

  1. Start your computer and enter BIOS setup.
  2. [An on-screen display or your manual will tell you how to this. With many BIOS's, you press *Delete* at boot-up.]
  3. Set the date to December 31st 1999 and the time to 11:59 p.m.
  4. Power down and turn off the computer for several minutes.
  5. Upon restarting the system, the date should roll over to Jan 1st 2000.
  6. If this is not the case, then your BIOS is not compliant.

Many manufacturers provide a "Y2K BIOS extender" file which can be installed in recent models computers to give a capability of going past the year 1999.

Be aware that some "BIOS Extenders" can interfere with virus detection and with being able to upgrade to another level of an operating system.

Major BIOS manufacturers are -

Further information is at - Year 2000 Reference;

The web site Mitre Corporation, gives links to most manufacturers that supply such files.

An excellent discussion of BIOS management is at Micro Firmware's article on "The Y2K Date Rollover Problem on PC Systems." by Terry Slade. That article's comments on the Windows operating systems are worth repeating here -

"... If the system is running under WIN3.1x over the century change, the date should roll over properly, just it would under DOS, but after rebooting the system it would show a date of 01-04-1980.

"Windows 95 also does not correct for the date rollover problem, although it may appear to if testing is not done carefully.

"Windows 98 does appear to correct for the date rollover problem, however this correction is thwarted if the system is booted from a DOS diskette on the first boot after the century change. The date would then be 01/04/80 and when Windows 98 is restarted it will keep this date until manually changed."

Also, it is worth repeating the experience on a U.S. Army Technology Integration Center page -

In two cases at our base, people downloading flash BIOS upgrades and installing them got the wrong BIOS [patch]. This resulted in disabling their PC. We did not have the capability to reprogram the BIOS chips, so we could not fix the problem without replacing the BIOS chip. It might be a good idea for you to put a disclaimer somewhere in the information on the BIOS upgrades that they must only be used on those specific PC configurations because they could damage other PCs. This is not a case in which someone can safely experiment to see if it works!

Plugin hardware modules are available that plug into DOS-type computers to extend the computer clock past the year 1999.

An example of such a module are available from -

Or a precision clock replacement card is available from -

Return to the top of the BCN Y2K BIOS page.

Real Time Clock (RTC) Discussion

The basic source of date information to a computer system is an integrated circuit called a Real Time Clock (RTC). This chip (until recently) used a 2 digit internal representation for the year that is translated into the 4 digit year code by the BIOS before it is forwarded to the OS and application software. Modern RTC chips are all Y2K compliant because they use a 4 digit representation of the year.

If you use a test program that tests everything OK except for the RTC, there is usually no need to worry, since those test programs do not take the subsequent BIOS date management into account. Most RTC software made after 1995 can usually be expected to be compliant given that the BIOS is compliant.

Return to the top of the BCN Y2K BIOS page.

Software for Diagnosing and Repairing Y2K Problems

Thr following programs are available to "diagnose" your system as to whether it is Y2K ready. Each of these sites has further information about how to proceed from there, or see - the Computer Operating Systems section in An Introduction to the Technical Side of the Y2K problem in this site to track down further information for your particular system.

Return to the top of the BCN Y2K BIOS page.

Return to top of the BCN Y2K home page.
Return to the BCN home page.
Please send any comments, additions or corrections about this Y2K center page to: y2k.
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Revised '27-Jun-2002,10:20:22'
URL of this page:
BCN/Y2K Center Coordinator: E. Stiltner