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HIERARCHICAL MEMORY
01
SYSTEM
02Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Memory Diagram
02Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Memory Diagram
It is a low-capacity, high-speed memory where data is temporarily stored. It is located in the CPU.
02Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Memory Diagram
It is a high-speed, small-capacity memory that is placed between the CPU or registers and the main memory.
02Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Memory Diagram
Referred as the ‘real memory’. DRAM is the predominant choice for implement computer main memory.
02Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Memory Diagram
The cache memory placed between a hard disk and the main memory.
02Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Memory Diagram
Devices that provide backup storage. The most common auxiliary memory devices used in computer systems are magnetic tapes and magnetic disks (hard disks)
02Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Memory Diagram
It is like a ‘second’ auxiliary memory. An example of a large-capacity memory is an optical disk.
02Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Memory Diagram
Additional: Remote memory – practically unlimited with varying speed. Examples are other computers and
internet (cloud)
Each level of the hierarchy is usually a
subset of the level below.
The memory hierarchy is organized into several levels of memory with the smaller, faster
memory levels closer to the CPU.
Data found in a level is also found in the level
below but at longer access time.
02Memory Diagram
Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Spe
edFast
Slow
02Memory Diagram
Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Pric
e
Expensive
Inexpensive
Spe
edFast
Slow
02Register
Cache Memory
Main Memory
Disk Cache
Auxiliary Memory
Large-Capacity Memory
Memory Diagram
The overall goal of memory hierarchy is to obtain the highest
possible average access speed while minimizing the total
cost of the entire memory system.
The concept is greatly aided by the principal of locality leading to
working set of a program.
03Principle of Locality
Also known as Locality of ReferenceThe phenomenon of the same value or related storage locations being frequently accessed.
90/10 Rule comes from the empirical
observation:“A program spends 90% of its time in 10% of its code.”
03Two Types of Access Locality
1. Temporal Locality2. Spatial Locality
Principle of Locality
031. Temporal Locality
Refers to the reuse of specific data and/or resources within relatively small time durations
Principle of Locality
Example: Instruction in the body of inner loops
032. Spatial Locality
Refers to the use of data elements within relatively close storage locations.
Principle of Locality
Example: Sequential instruction executions, sequential access
to elements of an arrays
032. Spatial Locality
Principle of Locality
Sequential locality, a special case of spatial locality, occurs when data elements are arranged and access linearly
Example: Traversing the elements in a one-dimentional
array
03Principle of Locality
System which exhibit strong locality of reference are good candidates for performance optimization through the use of techniques like the cache and instruction prefetch technology for memory or the advanced branch predictor at the pipelining of processors.
04Program Working Set
The “working set” is short hand for “parts of memory that the current algorithm is using”Any instant of time where programs usually access a relatively small portion of their address space (instruction/data).
04Program Working Set
Program Instruction Address Space Program Data Address Space
05
