In a prior blog, I wrote about the JTAG specification’s upcoming 30th anniversary, and reflected on how it has evolved over the years, and the powerful use cases it can be put to. This week, we look at how to secure the JTAG interface, to prevent its abuse by bad actors.
JTAG is coming up on its 30th anniversary. And some would say it’s older than that. As I prepared for doing an introductory presentation on this amazing technology, I got a chance to reflect on how useful it has become, and what the next 30 years might be like.
In my last article, I outlined a short embedded JTAG-based ‘C’ routine to dump machine check errors in the event of a system crash or hang. In today’s blog, I look at this in the larger context of diagnosing the root cause of system wedges, and what embedded ITP techniques can be used to gather as much forensics data as possible.
ASSET implements in-situ diagnostics via direct support of the x86 JTAG-based run-control API down on the target. The run-control API are synonymous with lower-level Intel In-Target Probe (ITP) procedures. What follows is a sample ‘C’ routine written to dump the contents of the machine check registers, in the event of a system wedge (for example, a three-strike event).
Moving run-control (Intel In-Target Probe, or ITP) down into the service processor on an x86 design results in a screamingly fast, scalable implementation of at-scale debug. This article contains some timing benchmarks of our embedded solution versus alternatives. The results are nothing short of astonishing.
In previous articles, I’ve written about the use of JTAG-based run-control for remote debug. Facebook presented an example of this a few weeks ago at the Open Compute Summit. This blog describes the real-time performance of such a BIST we designed for PCI Express link training tests.
Embedding JTAG into a system’s service processor allows for powerful out-of-band (independent of the operating system) built-in self test (BIST) functions. Using JTAG-based boundary scan, for example, can isolate system failure root cause to an extent unachievable through any other means.