Here is one estimate of 50 million noncompliant chips. Of course, no one knows. But the thought of 50 million failures happening all at once is mind-boggling. If any significant percentage hits public utilities and energy supply lines, these failures will be catastrophic.
This is taken from "The Year 2000 Crisis: An Enormous Challenge that Must be Addressed"
Strategic Analysis Report from the Gartner Group
D. Brown, W. Close, B. Conway, C. Germann, C. Goodhue, B. Hall, M. Hotle, C. Jones, N. Jones, H. Kline, M. Light, S. Nelson, J. Pucciarelli, B. Reilly, J. Seay, P. Sondergaard, B. Stanco, R. Terdiman, E. Andren
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Strategic Planning Assumption: More than 50 million embedded-system devices worldwide will exhibit year 2000 date anomalies in 1999 (0.6 probability).
The challenge that these devices pose is not restricted to IS organizations or IT applications. Most of the computers in the world are performing non-IT functions. In 1995, Dataquest, a Gartner Group company, estimated worldwide shipments of reduced instruction set computer (RISC) and x86 microprocessors at more than 200 million units -- over half of which were in embedded systems.