Browse Prior Art Database

Steering the Processor Reset Vector According to the System State

IP.com Disclosure Number: IPCOM000132461D
Publication Date: 2005-Dec-17
Document File: 3 page(s) / 39K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a BIOS redirection function that uses a 32-bit register to program the BIOS with a “CPU Only Reset” vector, once system initialization is complete. Benefits include resuming operation in a standard way across processor families and platforms.

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Steering the Processor Reset Vector According to the

System

State

Disclosed is a method for a BIOS redirection function that uses a 32-bit register to program the BIOS with a “CPU Only Reset” vector, once system initialization is complete. Benefits include

resuming operation in a standard way across processor families and platforms.

Background

Processors save power by reducing frequency, and removing power from unneeded functions during periods of light processor loading. The smallest amount of power is consumed when the processor is fully powered off. However, when a processor is fully powered off, the BIOS code that is invoked when power is restored is left with the problem of determining whether the system has been fully off, or whether only the processor has had power removed.  In the former case, the BIOS code is responsible for configuring the entire system, including memory, parameters, and I/O configurations. In the latter, the CPU is only responsible for restoring its own state, since the rest of the system may be assumed to have retained its state while the CPU lost power.

One way to approach the above problem is to leverage the fact that the processor’s first instruction is fetched from a fixed location near the top of memory. Since that fetch is accomplished through the chipset, the chipset is able to intervene and provide a different initial instruction. An earlier iteration of BIOS code can program a specific jump vector into the chipset, and the chipset...