US 7502958

US patent 7502958, titled "System and method for providing firmware recoverable lockstep protection," addresses the challenge of managing errors in lockstep processor systems without causing a system crash.

Summary of US Patent 7502958:

• Title: System and method for providing firmware recoverable lockstep protection
• Current Assignee: Foras Technologies Ltd
• Original Assignee: Hewlett Packard Development Co LP
• Inventors: Scott L. Michaelis, Anurupa Rajkumari, William B. McHardy
• Filing Date: 2004-10-25
• Issue Date: 2009-03-10
• Abstract: The patent describes a method for handling "loss of lockstep" (LOL) in a pair of processors. This method involves firmware detecting LOL, then triggering an operating system (OS) to idle the affected processors. The firmware then recovers the lockstep between the processors. Once recovery is successful, the firmware triggers the OS to recognize the processors as available for receiving instructions again.

Plain-Language Overview of Independent Claims:

• Independent Claim 1: This claim outlines a firmware-driven method for recovering from a "loss of lockstep" (LOL) in a pair of processors. Upon detecting LOL, the firmware first checks if the problem is "recoverable" by specifically determining if a "lockstep mismatch" has occurred (where the outputs of the two processors differ). If it's recoverable, the firmware directs the operating system to temporarily stop using these processors, then fixes the lockstep issue, and finally signals the operating system that the processors are ready to resume operations.
• Independent Claim 13: This claim describes a system comprising an Advanced Configuration and Power Interface (ACPI)-compatible operating system, a master processor, a slave processor (operating in lockstep with the master), and firmware. When this firmware detects a loss of lockstep between the master and slave processors, it uses an ACPI standard method to tell the operating system to idle the master processor. The firmware then attempts to restore the lockstep. If successful, it uses another ACPI method to inform the operating system that the master processor is available for use again.
• Independent Claim 19: This claim focuses on a system that includes a pair of lockstep processors and computer-executable firmware code. When a loss of lockstep is detected, the firmware code determines if the issue is recoverable, specifically by checking if a lockstep mismatch has occurred. If the lockstep is deemed recoverable, the firmware code triggers the operating system to idle the processors, then attempts to restore lockstep. If this recovery is successful, the firmware code informs the operating system that the processors are ready to receive instructions once more.
• Independent Claim 23: This claim describes a method for a multi-processor system, particularly for handling loss of lockstep involving the system's "boot processor." It starts by establishing a "hot spare" processor specifically for the boot processor. When a loss of lockstep is detected for any lockstep pair, the method determines if the affected pair is the boot processor. If it is the boot processor, the "good" state of the boot processor is copied to the hot spare, making the hot spare the new boot processor. If the affected pair is not the boot processor, the method proceeds by triggering the operating system to idle those processors, attempting to recover lockstep, and if successful, triggering the operating system to recognize them as available.

CAFC 2026 Dockets:
A search for US patent 7502958 in CAFC 2026 dockets did not specifically identify any cases directly involving this patent in the year 2026. While Google Patents indicates that the patent family has ongoing litigation, including a US case filed in the Court of Appeals for the Federal Circuit (case/25-1968), the available search results for specific 2026 CAFC dockets do not list US7502958 or its case number. Therefore, there is no authoritative information from the provided search results to confirm active CAFC litigation specifically for US7502958 within the 2026 timeframe.