William Stallings Computer Organization and Architecture

Memory

Terminologi

Memory cell Memory Word Byte Address Volatile Memory Write and Read Operation

Memori Cell Operation

Diagram Memori

Characteristics

Location Capacity Unit of transfer Access method Performance Physical type Physical characteristics

Location

CPU Internal External

Capacity

Internal memory : a byte a word in 8, 16, 32 bit

External memory a byte

Unit of Transfer

Internal in a word or larger, such as 16, 128,

256 External

Usually a block which is much larger than a word

Access Methods (1)

Sequential Memory is organized into unit of data : record. Access must be made in a specific linear

sequence Store addressing information is used to separate

record and assist in the retrieval process. Access time depends on location of data e.g. tape

Access Methods (2)

Direct Memory is organized into blocks Individual blocks have unique address Access is by jumping to vicinity plus

sequential search Access time depends on location e.g. disk

Access methode (3) Random

Individual addresses identify locations exactly Access time is independent of location e.g. RAM

Associative (4) Data is located by a comparison with contents of a

portion of the store A word is retrieved based on a portion of its content

rather than its address Access time is independent of location e.g. cache

Performance

Access time Time between presenting the address

and getting the valid data Memory Cycle time

Time may be required for the memory to “recover” before next access

Cycle time is access + recovery Transfer Rate

Rate at which data can be moved

Physical Types

Semiconductor RAM ROM

Magnetic Disk & Tape

Optical CD & DVD

Others Bubble Hologram

Physical Characteristics

Volatility Erasable Power consumption

The Bottom Line

How much? Capacity

How fast? Time is money

How expensive?

So you want fast?

It is possible to build a computer which uses only static RAM (see later)

This would be very fast This would need no cache

How can you cache cache? This would cost a very large

amount

Memory Hierarchy

Registers In CPU

Internal or Main memory RAM

External memory Backing store

Hierarchy List

Registers L1 Cache L2 Cache Main memory Disk Optical Tape

Memory Hierarchy - Diagram