Mips Technologies R4000 - Page 22

Table of Contents
xxii MIPS R4000 Microprocessor User's Manual
11
Cache Organization, Operation, and Coherency
Memory Organization.............................................................................................244
Overview of Cache Operations.............................................................................. 245
R4000 Cache Description.........................................................................................246
Secondary Cache Size.......................................................................................... 248
Variable-Length Cache Lines ............................................................................. 248
Cache Organization and Accessibility..............................................................248
Organization of the Primary Instruction Cache (I-Cache)......................... 249
Organization of the Primary Data Cache (D-Cache).................................. 250
Accessing the Primary Caches....................................................................... 251
Organization of the Secondary Cache .......................................................... 252
Accessing the Secondary Cache.....................................................................254
Cache States...............................................................................................................255
Primary Cache States...........................................................................................256
Secondary Cache States.......................................................................................256
Mapping States Between Caches....................................................................... 257
Cache Line Ownership............................................................................................258
Cache Write Policy...................................................................................................259
Cache State Transition Diagrams...........................................................................260
Cache Coherency Overview ................................................................................... 264
Cache Coherency Attributes...............................................................................264
Uncached ..........................................................................................................265
Noncoherent..................................................................................................... 265
Sharable............................................................................................................. 265
Update............................................................................................................... 265
Exclusive ........................................................................................................... 266
Cache Operation Modes...................................................................................... 266
Secondary-Cache Mode..................................................................................266
No-Secondary-Cache Mode ...........................................................................266
Strong Ordering ...................................................................................................267
An Example of Strong Ordering.................................................................... 267
Testing for Strong Ordering........................................................................... 267
Restarting the Processor .................................................................................268
Maintaining Coherency on Loads and Stores......................................................269
Manipulation of the Cache by an External Agent...............................................270
Invalidate...............................................................................................................270
Update ...................................................................................................................270