The Unabridged Pentium 4 IA32 Processor Genealogy

Test Access Port (TAP)

General

The Pentium® processor implemented the IEEE 1149.1 TAP and boundary scan architecture. It should be noted that a detailed discussion of the TAP and boundary scan is outside the scope of this publication. This decision was made for two reasons:

• The Pentium® processor data book contains a discussion of these features.

• The test engineering community is already well-acquainted with the IEEE 1149.1 spec.

The TAP provided access to both the boundary scan interface and the Pentium® processor's Probe Mode instruction and data registers. Probe Mode was included to implement debug tools (e.g., the Intel® In-Target Probe Tool) used to debug the system and software.

The processor's BIST (Built-In Self-Test) could be initiated ...