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Automatic Hardware Detection of Personal Computer Software System Resets and Re-Initial Program Load

IP.com Disclosure Number: IPCOM000034191D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 99K

Publishing Venue

IBM

Related People

Corkell, AF: AUTHOR [+4]

Abstract

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.

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Automatic Hardware Detection of Personal Computer Software System Resets and Re-Initial Program Load

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. The PC performs diagnostics during re- IPLs. The PC searches every 2048 bytes of ROS area for special characters. If, by accident, these characters exist in the attachment card's RAM, the PC will try to execute the bytes that follow, which would lead to a PC failure if these bytes were not microcode. The same problem occurs on power-up. In addition, for intelligent communication adapter cards, a system reset may be important information to pass to an upstream device, such as a main frame. Such information could be used to re-IPL the PC through the communications line. In the past, intelligent I/O cards deactivate their RAM from the PC bus upon power- up, but do not address the CAD sequence problem nor re-IPL the PC without explicit command from the PC. The I/O attachment card circuit of this disclosure is shown in the block diagram in Fig. 1. The I/O card is capable of...