JTAG was originally developed to solve board interconnect test problems and has evolved into a widespread and generic soft access test mechanism for chips, boards and systems. Examples includes reading internal registers and chip ID-codes, program flash memories, run BIST and embedded instruments thru IJTAG.

Bringing up prototype circuit boards is a tipping point in the product development cycle. Unfortunately, it too often becomes a tripping point. Boards that won’t come up can derail the project entirely, delaying the launch of the product into the market and generating staggering opportunity costs. Board bring-up must verify the functionality of the hardware so that application software can be loaded and debugged. Without a known-good-board, diagnosing software bugs would be futile.

This paper begins with an executive summary of embedded diagnostics, followed by an introduction to the 9's concept for highly-available systems, and then documents a number of case studies. It subsequently looks into the cost of server downtime and concludes with a section on future developments for high-availability systems.