Test features

The public instructions and some of the private instructions were implemented. A total of 85 instructions with additional logic in the chip core and I/Os provided control for key features such as internal scan, clock, I/O test and characterization. The support of public and private instructions had to be heavily customized, while being IEEE Std. 1149.1 compliant. The reason for this was the design of very high speed I/Os in UltraSPARC-III. Public instructions are mainly used for device identification and circuit board testing. Private instructions are primarily used to gain access to features used to aid in manufacturing based testing, failure analysis and debugging. All test features of the processor are carried out through the test access port.