Browse Prior Art Database

Method For Rerouted Error Display Using Code-Forced Alternate Error

IP.com Disclosure Number: IPCOM000012859D
Original Publication Date: 2003-Jun-04
Included in the Prior Art Database: 2003-Jun-04
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Abstract

This describes a method for using an alternate route to detect an error and display error information on the service processor-attached display panel.

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Method For Rerouted Error Display Using Code-Forced Alternate Error

The display panel on a Regatta system is part of the service processor, whose multipurpose access chip is attached to a PCI host bridge (PHB), which in turn is attached to an I/O hub, which in turn is attached to a system processor. The problem is that an I/O error somewhere in the main resource path between the PHB and the service processor/display panel causes the PHB to freeze and prevents regular I/O access to it (the only way the service processor is able to be notified of PHB errors). Firmware running on the system processor cannot get to important system resources like the service processor or the panel via normal I/O since the path is inaccessible; if firmware tries to access a system resource while it is in error state, it causes a second machine check which puts the system into checkstop state with "imprecise error information". Firmware cannot reset the PHB from error state, since it might result in a data integrity exposure (other processors in the system continue to run for awhile until they also can't get to the main system resources). Fortunately, there is another way for the system processor to get the service processor's attention. This invention makes use of this feature and adds a new technique to convey the "precise error information" needed by the diagnostic code running on the service processor, enabling it to correctly isolate and report the root of the problem.

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