Chapter 4 Flashcards
The Memory Hierarchy: Locality and Performance
Define
Principles of Locality
Observation that during the course of execution of a program, memory references by processor tend to cluster. Makes effective use of a memory hierarchy possible.
List
The 3 assertions Principle of Locality is based on
- During any interval of time, a program references memory location non-uniformly
- As a function of time, the probability that a given unit of memory is referenced tends to change slowly
- The correlation between immediate past and immediate future memory patterns is high and tapers off as time interval increases
List and define
The 2 forms of locality
- Temporal- refers to tendency of a program to reference in the near future those units of memory referenced in the recent past (Const, temporary variables, working stacks)
- Spatial- tendency to reference units of memory whose addresses are near one another. Also reflects tendency of program to access data locations sequentially
List
Key Characteristics of Computer Memory Systems
Location (internal and external)
Capacity
Unit of Transfer
Access Method
Performance
Physical Type
Physical Characteristic
Organization
Define
Unit of Transfer
In Memory System
Internal, equal to number of electrical lines in and out of memory module
List
Access Methods
In Memory System
Sequential
Direct
Random
Associative
List
Physical Types
In Memory System
Semiconductor
Magnetic
Optical
Magneto-optical
List
2 most important characteristics of memory
Capacity
Performance
List
3 performance parameters used for Capacity and Performance
In Memory System
Access Time (latency)
Memory Cycle Time
Transfer Rate
Define
Memory Cycle Time
In Memory System
Access time + any additional time before second access can commence. Concerned with system bus, not processor
List
Memory Design Constraint Questions
How much
How fast
How expensive
trade offs
Define
Inclusion Principle
In Memory System
Dictates that all information items are originally stored in level M_n, where n is the level most remote from the processor.
