I've been doing a lot of reading about Y2K in general, but I still think a great deal of my information is spotty. I've read that some systems in a power grid (Such as boilers) run two systems, a command console PC and a PLC each with an real time clock. These systems can also have the chance of thinking its 1980. How valid is this information?

-- Anonymous, October 28, 1998

Answers

Completely Valid. In most (>95%) of IBM PC compatible embedded systems (and many PLCs) the realtime clock is provided by a Motorola (or compatible) chip. The chip only has a 2 digit year and hence rolls the date over to 1900 at the turn of the century. The way the PC BIOS and operating system interpret this incorrect hardware date is where all the variations of the Y2K bug stem from.

When the PC BIOS reads the date 1/1/1900 it "knows" this is an invalid date and so sets it to a default value. The default can be the date of that version of the BIOS code eg. "4/3/1986", or an arbitrary start date "1/1/1980" or a completely bizarre date such as "2/19/2106" caused by an internal date calculation error.

For more about PC clocks see my comments in these threads in this forum: Gartner report (1998-10-12) Crouch/Echlin and Power Utilities - Is this being considered? (1998-10-29)

--AJ

-- Anonymous, October 30, 1998