On-chip bugs for debug

The moment a chip arrives back from the fab is always tense. Once the first piece of silicon is down on the board and things check out electrically the thing to do is work out whether it really is an advanced system-on-chip (SoC) or a silicon-and-glass sandwich. Conceptually, the process is similar to the trace buffers used on many embedded processors. They do not capture actual instructions but record whether branches were taken or not. A debugger takes the data out through a test port and then uses it to reconstruct what happened inside the processor and display the instruction trace to the developer. With logic debug, the problem is more complex as there are so many different types of signal on the chip - not just a stream of instructions. But Novas's Siloti tool will use the recorded data in a similar way and attempt to show which signals changed during a given period.