The last-second switch also introduced a giant vulnerability - the error trap ("panic handler") code in the Xbox's "Secret ROM" was intended to disable access t

The last-second switch also introduced a giant vulnerability - the error trap ("panic handler") code in the Xbox's "Secret ROM" was intended to disable access to the Secret ROM and halt. Of course, this was a challenge as disabling the Secret ROM would also prevent the Halt instruction from being read. So, instead, the error trap was placed at the end of the mapped address space, and relied on EIP overflowing to 0x0 afterwards and causing a double fault, which would halt the CPU. This was true for AMD CPUs, but for Intel CPUs, false - they'd just roll over and restart execution at 0x0. This was the so-called "visor" exploit which enabled unencrypted bootloader payloads.