Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

MULTIPLE INTERNAL BUS RESERVATION SNOOPING IMPLEMENTATION

IP.com Disclosure Number: IPCOM000008907D
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2002-Jul-23
Document File: 2 page(s) / 74K

Publishing Venue

Motorola

Related People

Tony Thompson: AUTHOR [+4]

Abstract

A cost-effective reservation snoop mechanism for a bus interface unit with multiple bidirectional buses and the capability of handling reservation des- tinations on all buses. A reservation can only be set from one of the buses but the reserved memory location can be on any bus. Further, the reserved location can be 'touched' by a write access originat- ing on any bus. Thus the mechanism must support all source/destination combinations for the intruding write cycles. Writes by the bus master that originally set the reservation are to be ignored.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 58% of the total text.

Page 1 of 2

0 M

'MOTOROLA Technical Developments

MULTIPLE INTERNAL BUS RESERVATION SNOOPING IMPLEMENTATION

by Tony Thompson, Ajay Nath, Bart Martinet and Guruswamy Ganesh

DEFINITION OF THE PROBLEM

  A cost-effective reservation snoop mechanism for a bus interface unit with multiple bidirectional buses and the capability of handling reservation des- tinations on all buses. A reservation can only be set from one of the buses but the reserved memory location can be on any bus. Further, the reserved location can be 'touched' by a write access originat- ing on any bus. Thus the mechanism must support all source/destination combinations for the intruding write cycles. Writes by the bus master that originally set the reservation are to be ignored.

DESCRIPTION OF PRIOR WORK BY OTHERS

  Prior PowerPC microcontrollers have reserva- tion snoopers for single buses located in caches (internal) or an external bus snooper. Cache- coherency snooping mechanisms do not have to deal with multiple bidirectional bus interfaces.

OUR SOLUTION

  Any modification (write access) to the reserved location will always be visible on the bus where the memory location resides, irrespective of the source bus of the access.

  The solution, therefore, is to snoop the destina- tion bus (bus where the reserved location resides), instead of parallel snooping all possible source buses. Since the reservation snooper is part of the a bus interface unit, the destination bus of a load- with-reservation access can be determin...