Browse Prior Art Database

Multipurpose Paged Writable Control Store

IP.com Disclosure Number: IPCOM000078235D
Original Publication Date: 1972-Dec-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Cocke, JE: AUTHOR [+2]

Abstract

Single writable control store 12 Performs the control functions conventionally distributed among the CPU, channels and control units.

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Multipurpose Paged Writable Control Store

Single writable control store 12 Performs the control functions conventionally distributed among the CPU, channels and control units.

Main memory 10 contains the conventional CPU programs, I/O channel programs and data. Main memory 10 contains an image of all the microcode of the system, i.e. routines for performing CPU functions, control unit functions, and I/O channel functions. The microcode is paged from main memory 10 to high- speed control store 12 as required and executed from there in microcode execution unit 16. High-speed local store 14 acts as a data memory for the microcode routines.

All communications with main memory 10 are through high-speed local store 14 or control store 12. Control store 12 contains a permanently resident routine to control the paging of the microcode. CPU instructions, channel commands and data are fetched from main memory 10 to local store 14 under the control of microcode executed in unit 16 from high-speed writable control store 12. The CPU instructions and channel commands are then interpreted or emulated, by appropriate routines executed in unit 16 from high-speed writable control store
12.

Replacement algorithms are handled by a paging control microprogram. Routines used frequently may never be overwritten in control store 12, yielding good performance. Routines controlling I/O devices 18 on communication line 20 are brought into control store 12 before the I/O operation begins an...