The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 18, 1998
Filed:
Jan. 14, 1997
David C Johnson, Roseville, MN (US);
Douglas A Fuller, Eagan, MN (US);
Kenneth L Engelbrecht, Blaine, MN (US);
Gregory A Marlan, San Jose, CA (US);
Ronald G Arnold, Apple Valley, MN (US);
Gerald G Fagerness, Mazeppa, MN (US);
Unisys Corporation, Blue Bell, PA (US);
Abstract
Method and apparatus for performing microcode paging during instruction execution in an instruction processor. In a preferred embodiment an instruction processor is provided that includes both a microcode ROM and a microcode RAM. The microcode ROM stores the current release of the microcode for the computer system, and the microcode RAM stores microcode patch instructions. During instruction execution, the present invention selects between the output of the microcode ROM and the microcode RAM, depending on whether the instruction requires a patch microcode instruction. If the desired microcode patch instruction is not stored in the microcode RAM, the instruction processor is temporarily interrupted and the desired microcode patch instruction or a group of microcode patch instructions are written, or paged, into the microcode RAM.