Finding a CPU design bug in the Xbox 360

The recent reveal of Meltdown and Spectre reminded me of the time I found a related design bug in the Xbox 360 CPU – a newly added instruction whose mere existence was dangerous.

Back in 2005 I was the Xbox 360 CPU guy. I lived and breathed that chip. I still have a 30-cm CPU wafer on my wall, and a four-foot poster of the CPU’s layout. I spent so much time understanding how that CPU’s pipelines worked that when I was asked to investigate some impossible crashes I was able to intuit how a design bug must be their cause. But first, some background…


  1. dionicio 2018-01-09 3:02 pm EST
  2. dionicio 2018-01-09 4:04 pm EST
  3. dionicio 2018-01-09 4:32 pm EST
  4. dionicio 2018-01-09 5:31 pm EST