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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