Automatic Hardware Detection of Personal Computer Software System Resets and Re-Initial Program Load
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-27
This article describes a circuit and technique for detection of personal computer (PC) software system resets and re-initial program load (IPL). (Image Omitted) Within the family of products of the PC, there exists only one way to reset the PC CPU. The operator must enter a keyboard sequence Ctrl- Alt-Del (CAD). This sequence is only a software-controlled reset. It does not activate the reset signal on the PC channel, but instead initiates a keyboard interrupt, which is then serviced by the PC CPU. The PC CPU analyzes the sequence, jumps to a specified read-only storage (ROS) location, and re-IPLs the system. I/O attachment cards have no indication that a re-IPL has occurred. This creates a problem for intelligent dual-ported memory mapped I/O attachment cards residing in the PC ROS reserved area.