The hardware team had some semi-custom thing from intel that spat out (no surprise) gigabytes of trace data per second. I remember much of the pain was in constructing a lab where we could drive a test system at reasonable loads to get the buggy behavior to emerge. It was intermittent so it took use a couple weeks to come up with theories, another couple days for testing and a week of analysis before we came up triggers that allowed us to capture the data that showed the bug. it was a bit of a production.