Digital Equipment Corporation

Peter C Schnorr

David N Cutler

Robert T Short

H Bruce Butts, Jr

A central processing unit for a digital computer. In one embodiment, the central processing unit comprises a plurality of pointer registers that may be used during instruction execution to directly address other registers. In a second embodiment, the central processing unit comprises a size register that is loaded during the decode of an operation code with a size code indicating the data path width for that operation code. During instruction execution, the size code may be used at various times to determine data path width.

Central processing unit for a digital computer

A central processing unit for a digital computer has a central memory unit connected to a system bus. A data path unit decodes variable length microinstructions that are stored in the central memory unit and that include an operation code and one or more operand specifiers, issuing a microaddress of one of a set of microinstructions stored in a control store. The microinstructions have a data path control field, a condition/size field and a next address control field. A microinstruction logic control is responsive to the microinstructions, and a memory control unit that includes a data cache memory array operates asynchronously with respect to the data path unit, translating virtual memory addresses to access data from the data cache memory array or from the central memory unit.

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Redmond, WA, United States of America

Peter C Schnorr