Important Notes
.... The user must make sure that the particular system has been tested and complies with the year 2000 date roll over prior to the year end 1999, and to satisfy himself/herself that both hardware and software will work correctly after that date.
The PC vendor 's current product range is now fully Year 2000 compliant. However in an extremely small number of cases, even brand new PC's, will fail to correctly enter the next millennium.
The PC vendor PC's, like all PC's, generally have three different clocks inside them; all running independently. These clocks are the CMOS, BIOS and OS (Operating System) timers. The lowest level clock is the CMOS clock and this is hard wired to only work from 1900 to 1999. After 1999 it resets automatically back to 1900. The BIOS clock, which takes its data at boot-up from the CMOS clock, has been made millennium compliant by spotting when the CMOS clock resets back to 1900. The BIOS clock then knows that it is the year 2000. The OS clock takes its data from the BIOS clock and so this clock will hold the correct data. So (after the year 2000) we have three clocks, two are correct but one is wrong.
Most software, including all the PC vendor supplied software, takes the date information from either the BIOS or OS clock and so all date information is correct. Some bespoke software packages read the date directly from the BIOS clock; again there is no date problem here.
The problem occurs when a software package reads its date information from the CMOS clock. In the year 2000, the CMOS will think it is 1900 and the problems are obvious. The types of software that use this method are still in use today, e.g. Data Acquisition, machine control etc. It must be said that the number of the PC vendor PC's using this kind of software is probably very small.
The problem with the CMOS clock affects all PC manufactures equally as the CMOS clock has not changed since the first IBM AT design.
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