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Patent Title: Method for expanding addressable memory range in real-mode processing to facilitate loading of large programs into high memory

Assignee: IBM
Patent Number: US5642491
Issue Date: 06-24-1997
Application Number:
File Date:09-21-1994

Abstract: Disclosed is a technique for overcoming the 1-Mbyte mode memory limitation associated with "real-mode" operation of certain Intel Corp. microprocessor architectures. This limitation can be overcome by altering the contents of a register portion that is computationally meaningful only in "protected mode," but which persists and exerts effects in real mode. By indirectly manipulating the contents of this register portion in protected mode in a manner that avoids disruption to the register during the switch back to real mode, access can be obtained, in real mode, to up to 4 Gbytes of volatile memory.

Notes:

Link to USPTO

IBM Pledge dated 1/11/2005