Checkpoint logging without checkpoint display device availability

摘要

A processor register is reserved by early firmware code to be employed for checkpoint logging or for storing diagnostic information at the time of failure before a checkpoint display device, usually contained within an I/O subsystem, is initialized. Early firmware codes are usually written in assembly language and the firmware of the present invention dedicates a processor register for logging checkpoint information. If a machine fails before any checkpoint, or point of failure, is displayed by a checkpoint display device, a dedicated processor register has logged any checkpoint or diagnostic information. The error information relating to the failure is obtained from the dedicated register through JTAG (Joint Task Action Group) scanning utilizing a processor debugging tool.