From The Register, so not sure how reliable. However if its true it will be interesting to see what people can do with it!
http://www.theregister.co.uk/2010/11/15/amd_secret_debugger/
Sorry if this is old, I couldn't see anything when I glanced at the front page.
http://www.theregister.co.uk/2010/11/15/amd_secret_debugger/
A hardware hacker has discovered a secret debugging feature hidden in all AMD chips made in the past decade.
The password-protected debugger came as a shock to reverse-engineers who have hungered for an on-chip mechanism for performing conditional and direct-hardware breakpoint operations
Sorry if this is old, I couldn't see anything when I glanced at the front page.