Browse Prior Art Database

Storage Protection in Small Processors

IP.com Disclosure Number: IPCOM000041356D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Borchsenius, E: AUTHOR [+2]

Abstract

Typical storage protection mechanisms prohibit one program from inadvertently overlaying its own or other program's storage locations in order to prevent a need to re-Initial Program Load (re-IPL) due to a program wandering off in an uncontrolled manner. On some small computers, storage protection is not implemented due to cost/function tradeoffs. The figure shows an adapter which is connected between the computer's I/O bus and the I/O devices, and which realizes the storage protection objective without the storage protect programming and hardware cost. Hardware Each adapter contains n hardware triggers (called "Allow Bits", one for each device it controls). When an Allow Bit is on, all write operations are rejected. When it is off, all operations work normally.

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Storage Protection in Small Processors

Typical storage protection mechanisms prohibit one program from inadvertently overlaying its own or other program's storage locations in order to prevent a need to re-Initial Program Load (re-IPL) due to a program wandering off in an uncontrolled manner. On some small computers, storage protection is not implemented due to cost/function tradeoffs. The figure shows an adapter which is connected between the computer's I/O bus and the I/O devices, and which realizes the storage protection objective without the storage protect programming and hardware cost. Hardware Each adapter contains n hardware triggers (called "Allow Bits", one for each device it controls). When an Allow Bit is on, all write operations are rejected. When it is off, all operations work normally. The Allow Bit triggers are set and reset under program control over the I/O bus and, in addition, can reset themselves after a device completion time period. Supporting Program Each adapter normally has an I/O control program associated with it which in turn is driven by a group of device-oriented applications. One program module associated with each adapter should be designed to statically or dynamically set its device's Allow Bit when an I/O write is imminent.

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