MEMORY INTERNAL

Characteristics of Memory Systems (in general)

1. Location

® CPU

® Internal (main)

® External (secondary)

2. Capacity

® word size

® The number of word

3. Transfer Unit

® Word

® Block

4. Access Methods

® Sequential access

® Direct access

® Random access

® Associative access

5. Performance

® Access time

® Cycle time

® Transfer rate

6. Physical Type

® Semiconductor

Surface magnetic ®

7. Physical Characteristics

® Volatile / nonvolatile

® Erasable / nonerasable

8. Organization

Note:

For users of memory are two important characteristics

Ø Capacity,

Ø Performance.

Explanation

Ad 1) Memory Locations

There are three locations in the presence of memory in computer systems, namely:

Ø Local Memory

o is a built-in memory in the CPU (microprocessor),

o This memory is required for all activities of the CPU,

o This memory called registers.

Ø Internal Memory

o Being outside of the CPU but is internal to the computer system,

o Required by the CPU to process execution (operation) program, so it can be directly accessed by the processor (CPU) without any intermediary module,

o The internal memory is often also referred to as primary memory or main memory.

o Internal memory usually use RAM media

Ø External memory

Characteristically o external to the computer system and of course is outside the CPU,

o Required to store data or instructions permanently.

o Not required in the execution process so it can not be accessed directly by the processor (CPU). To access this external memory by the CPU to go through the controller / module I / O.

o External memory is often also referred to as the secondary memory.

o This memory consists of peripherals such as storage devices: disks, magnetic tapes, etc..

Ad 2) Memory Capacity

Ø Capacity of registers (local memory) is expressed in bits.

Ø Internal memory capacity is usually expressed in terms of bytes (1 byte = 8 bits) or word. Common word length is 8, 16, and 32 bits.

Ø external memory capacity is usually expressed in bytes.

Ad 3) Transfer Unit (Unit of Transfer)

Transfer unit equal to the number of channels incoming data into and out of memory modules.

Ø For the internal memory (main memory), the transfer unit is the number of bits that is read or written into memory at a time.

Ø For external memory, data is transferred in a far greater number of word, in this case is known as a block.

Word

Word size is usually equal to the number of bits used for representation of numbers and the length of the instruction, unless the CRAY-1 and VAX.

Ø CRAY-1 has a word length of 64 bits, using 24-bit integer representation.

Ø VAX instructions that varied in length, wordnya size is 32 bits.

Addressable Units

In some systems, addressable unit is the word. The relationship between the length of an address (A) by the number of addressable units (N) is 2A = N

Ad 4) Memory Access Methods

There are four types of data access unit, as follows.:

Ø Sequential Access

Ø Direct Access

Ø Random Access

Ø Associative Access

v Sequential Access

® Memory is organized into units of data, called records.

Access ® is made in the form of a specific linear sequence.

® addressing information is used to separate the records and to assist the search process.

® Mechanism of read / write is shared (shared read / write mechanism), by walking towards the desired location to remove the record.

® Time access records vary widely.

® Example of sequential access is access to magnetic tape.

v Direct Access

® As with sequential access, direct access also make use of shared read / write mechanism, but each block and the record has a unique address based on physical location.

® Access is done directly against the general range (general vicinity) to reach the final location.

® access time varies.

® Example of direct access is access to the disk.

v Random Access

® Each location can be selected at random and are directly accessible and addressable.

® The time to access a particular location does not depend on the access sequence in advance and are constant.

® An example is a system of random access main memory.

v Associative Access

® Each word can be searched based on content and not by address.

As with RAM ®, each location has its own pengalamatannya mechanism.

® Time is a constant quest does not depend on the location or the previous access pattern.

® Example associative cache is a memory access.

Ad 5) Performance Memory

There are three parameters to the memory system performance, namely:

Ø Time Access (Access Time)

® For RAM, access time is the time required to perform a read or write operation.

® For the non-RAM, access time is the time required to perform read and write mechanism at a specific location.

Ø Cycle Time (Cycle Time)

® The cycle time is the access time plus the time of the transient until the signal is lost from the channel to produce a return signal or data when data is read destructively.

Ø The rate of transfer (Transfer Rate)

® Transfer rate is the speed of the transfer of data to be transferred from the memory unit or memory unit.

® For RAM, the transfer rate is equal to 1 / (cycle time).

® For a non-RAM, apply the following equation.:

TN = average time to read or write the number of N bits.

TA = average access time

N = Number of bits

R = The transfer speed, in bits per second (bps)

Ad 6) Type of Physical Memory

There are two types of physical memory, namely:

Ø semiconductor memory, this memory technology using LSI or VLSI (very large scale integration).

This memory is widely used for internal memory such as RAM.

Ø Memory magnetic surface, this memory is widely used for the external memory to disk or magnetic tape.

Ad 7) Physical Characteristics

There are two criteria that reflect the physical characteristics of memory, namely:

Ø Volatile and Non-volatile

o The volatile memory, the information will naturally damaged or lost when electrical power is turned off.

o In non-volatile memory, once the information recorded will still be there without damage prior to the change. In this memory power is not required to maintain such information.

The memory is non volatile magnetic surface.

Semiconductor memory may be volatile or non volatile.

Ø Non-erasable Erasable and

o Erasable memory means that the contents can be removed and replaced with other information.

o The semiconductor memory that is not eliminated and is non-volatile ROM.

Ad 8) Organizations

What is meant by the organization is setting up the bits in the physical word.

Memory Hierarchy

Three questions in the design of memory, namely:

How much? How fast? How expensive?

Capacity. When an access price

Each spectrum technology has the following relationship.:

Ø The smaller the access time, the greater the price per bit.

Ø The larger the capacity, the smaller the price per bit.

Ø The larger the capacity, the greater the access time.

To get the best performance, memory should be able to follow the CPU. This means that if the CPU is executing instructions, we do not need to stop the CPU to wait for instructions or operands.

To get the best performance, memory becomes expensive, berkasitas relatively low, and a fast access time.

To obtain optimal performance, memory components need to be a combination of technologies. From this combination of memory hierarchy can be structured as follows.:

Decreasing hierarchy, then the things below will occur:

a) Decrease in price per bit

b) Capacity

c) Increased access time

d) Decrease the frequency of memory access by the CPU.

The key to organizational success is a decrease in the frequency of memory access by the CPU.

If the memory can be organized with a reduction in price per bit by increasing access time, and when the data and instructions can be distributed through this memory with a reduced frequency of memory access by the CPU, then this pattern will reduce the overall cost secar with specific performance levels.

Register is a type of memory the fastest, smallest, and most expensive is the internal memory to the processor.

The main memory is an internal system memory of a computer. Each location in main memory has a unique address.

Cache is a device for movement of data between main memory and processor registers to improve performance.

All three forms are volatile meori above and use of semiconductor technology.

Magnetic disk and magnetic tape is the external memory and is non-volatile.

Memory Semiconductors

There are some memory semiconductors, namely:

1. RAM: Static RAM (SRAM) and dynamic RAM (DRAM).

2. ROM: ROM, programmable ROM (PROM), Erasable PROM (EPROM), electrically EPROM (EEPROM), Flash Memory.

Random Access Memory (RAM)

Ø Read and write data to and from memory can be done easily and quickly.

Ø Characteristically volatile

Ø Keep the mains power supply.

Dynamic RAM (DRAM)

Compiled by the cells that store data as electrical charge on the capacitor.

There is and there is no electrical charge on the capacitor is expressed as binary numbers 1 and 0.

Keep charging the electric charge periodically to maintain data penyimapanan.

Static RAM (SRAM)

Compiled by a row of flip-flop.

Both SRAM and DRAM are volatile. DRAM memory cell is simpler than SRAM, because it's smaller. DRAM is more tightly (smaller cells = more cells per unit area) and cheaper. Goes a charge pengosong DRAM circuit. DRAM tends to be better when used for the larger memory requirements. Slower DRAM.

Read Only Memory (ROM)

Ø Storing data permanently

Ø It can be read

Two problems ROM

Ø Step insertion of data requires high fixed costs.

Ø It should not be in error (error).

Programmabel ROM (PROM)

Is non volatile and can only be written once.

The process of writing formed electrically.

Special equipment required for the process of writing or "programming".

Erasable PROM (EPROM)

Be read optically and electrically writeable.

Before the write operation, all storage cells must be removed using ultra-violet radiation of the chip package.

Removal process can be performed repeatedly, each deletion takes 20 minutes.

For the same data capacity is more expensive than PROM EPROM.

Electrically EPROM (EEPROM)

Can be written at any time without deleting the previous contents.

Watu write operation requires longer than read operations.

Combined non-volatility of excess properties and the flexibility to update by using the bus control, address and data lines.

EEPROM is more expensive than EPROM.

Memory cells have certain properties as follows.:

Ø It has two stable conditions for the representation of binary 1 or 0.

Ø Has the ability to write

Ø Has the ability to read.

Logical organization Chips (Chip Logic) Memory

16 Mbit DRAM organizations in general. Memory array is organized as four elements kuardrat 2048 to 2048. Aray elements connected by horizontal lines (rows) and vertical (column). Any horizontal line connected to the terminal Data-in/Sense each cell in column