For circuit board manufacturers, a self-healing bus like Intel® QPI can be self-defeating. Especially when it comes to board quality and diagnosing structural defects. Functional tests will typically not detect QPI faults like shorts and opens because they can be hidden by QPI’s self-repairing capabilities. Often, QPI buses with structural faults will train up well enough to slip through functional testing, only to manifest user problems later like reduced performance, more lane drop-outs, hangs and others.
Unlike traditional functional test and probe-based test methods like in-circuit test (ICT), which causes signal integrity problems on QPI, JTAG / boundary-scan diagnostics applied through the Intel XDP interface or custom JTAG hardware pinpoints structural problems on QPI.
This eBook shows how JTAG / boundary-scan tests improve manufacturing quality by isolating structural faults on QPI.