Finding a CPU Design Bug in the Xbox 360

I'm now wondering if I have enough material to do an interesting writeup for my time as a CPU bug-hunter in verification. The client (a now vanished startup) had a small 8-bit CPU design which they wanted validation for, using the technique of executing random sequences of instructions and comparing the result against an emulator. We wrote the emulator independently from their architecture description. Given that most instructions were a single byte plus arguments and most of those were valid…

Bruce Dawson taught a 100 level class at the college I attended, it's been a while but I think the class title was something around image processing. The first or second assignment was to copy one image region into another, little did we know that we implemented bit blit. After turning in the assignment the next class he grabbed one random assignment from the class and added some quick benchmark instrumentation and if I remember right then asked the class…

It is interesting that IBM dominated this generation of consoles, and was vanquished in the next. The high failure rates of the Xbox 360 did not help. https://en.wikipedia.org/wiki/Xbox_360_technical_problems

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