Apparatus for determining during a power-on sequence, a value to be written to a first register in a secure area and the same value to a second register in non-secure area, which during a protected mode, the value is compared such that if it is equal, enabling writing to a memory

Abstract

Systems and methods of securely updating BIOS are disclosed. One such system comprises a reprogrammable memory, a first and a second register, and comparison logic. The reprogrammable memory comprises a first portion and a protect input. The protect input is configured to disallow writes to at least the first portion when the memory protect input is at a first level, and to allow writes to at least the first portion when the protect input is at a second level; The comparison logic is configured to drive a comparison output to a third level responsive to the first and second registers having equal values, and to drive the comparison output to a fourth level responsive to the first and second registers having different values. The comparison output is electrically coupled to the memory protect input.