What's next for HSST?
Do we expect CPU core speeds to increase by 300 percent in the next few years? They may, but what is definite is that higher levels of integration in SoC designs will output more trace data than ever, even if CPU core speeds remain constant.

Multi-core designs will output more trace data and programmers will increasingly depend on trace to solve the significantly more difficult problems we will create with multi-core systems.

Timing problems will only increase, because we now have true asynchronicity with independent CPUs running, instead of just the simulated asynchronicity we have with single-chip multitasking. Trace protocols must include some way of synchronizing and correlating trace data collected from multiple cores.

SoCs will also have configurable logic, like FPGA fabrics, as well as specialized processors to handle application-specific tasks. These devices need debugging as well, and will also output trace data along with normal CPU data.

ARM's Coresight system already provides a mechanism for combining multiple sources of trace data on an SoC for output in a single trace stream to a trace collection probe. We now need to provide enough bandwidth for this data. Fortunately, it's relatively straightforward to use a high-speed serial interface for these systems.

A serializing module on the parallel outputs of an ARM Coresight port, for example, outputs high-speed serial data to a serial receiver which will convert the serial stream back into parallel Coresight data. From the parallel trace port's point-of-view, nothing has changed except for a huge bandwidth increase.

And this is not an over-simplification of HSST implementation either as the first prototype systems used exactly this scheme. A conventional parallel trace system was connected to a serializer that sent its output over a cable to a deserializer that fed a conventional parallel trace collection probe.

The parallel-trace tools had no idea that such a conversion was being done, and worked, more or less. Of course, over time, more direct integration will see systems transmitting serial trace directly instead of attaching very expensive serial transceivers to existing systems, but the concept does work in actual use.

It's an exciting time to be in the debugging tools business: we are on the cusp of a very big change in the capabilities of our tools as they start to make debugging of traditionally very difficult problems manageable.

Andre Yew manages Green Hills Software's Target Connections group, which connects the MULTI Integrated Development Environment to hardware targets. The group is responsible for Green Hills' debug devices, and its supporting software. Andre has a Bachelor of Science in Engineering and Applied Science from the California Institute of Technology.