Discussion About Computer Memory (Informatics Engineering)

computer memory

Hello friends, here I will briefly review the lecture material that I used to get when I was still struggling to study Strata 1 in the Informatics Study Program. Even though I’m not very smart, here I’m just sharing material during lectures.. ^_^

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In this discussion we will review about Memory / Storage Methods in a computer. Please note, maybe for some people think that the so-called hard disk storage is, yes it is, but it’s not that simple… even in processing data on a computer CPU there is a fairly complex method related to memory… whether it’s temporary storage to be forwarded to other parts, or permanent storage as a form of cache to facilitate data retrieval

In terms of informatics science, there are 2 divisions of memory, namely Internal memory (RAM) and External Memory (Hardisk, CD ROM, Magnetic Tape, Diskette), but here we will discuss the internal one more…


Before going any further, we need to understand Memory Hierarchy


  • enhancement access
    memory (the lower the slower, the higher the faster)
  • enhancement capacity (going down is getting bigger, going up is getting smaller)
  • enhancement distance with processor (the further down the further, the further up the closer)
  • drop memory price per bit (the lower the cheaper, the higher the more expensive)

Characteristics of the Memory Hierarchy

The further down, the hierarchical triangle has the following properties:

1. The lower you go, the cheaper the price per BIT

  • Registers are the most expensive type of memory
  • Cheapest Magnetic Tape and CD-ROM

2. The lower you go, the bigger the capacity size

  • Register capacity size is very small, namely in: 8bit…128bit
  • Magnetic Tape , CD, DVD-ROM in Giga Bytes


The lower you go, the slower the data access.

  • Register very fast data access
  • Magnetic tape is very slow to access data.

4. The lower you go, the less CPU access you have

  • The register is almost always accessed by the CPU
  • Magnetic Tape, CD-ROM is very rarely accessed by CPU


on the location memory can be divided into 3 types:

  1. Processor Memory (example: registers)
  2. Main Memory (example: RAM)
  3. External Memory (example: Hard Disk, RAID , CD-ROM, Tape)

Based on Physical, there are 3 Types of Memory

  1. Semi-conductor Memory Example: RAM, ROM, EEPROM, FLASH
  2. Magnetic Memory Example: Hard Disk, Diskette, Magnetic Tape
  3. Optical Memory Example: CD/R , CD/RW, DVD

Memory Access Method

There are 4 types of data unit access, as follows:

  • Sequential Access
  • Direct Access
  • Random Access
  • Associative Access

1. Sequential Access Method

  • Memory is organized into units of data, called record.
  • Data access is carried out in a specific (linear) sequence, such as on magnetic tape
  • Data access is very slow, because the data to be accessed is serialized one by one.
  • Addressing information is used to separate records and to assist the search process.
  • The read/write mechanism is shared (shared
    read/write mechanism
    ), by walking to the desired location to output the record.

Example: Magnetic Tape Back Up Cartridge

2. Direct Access Method

  • Data access is done directly, based on track and sector positions
  • Data access is relatively faster, compared to Sequential Access

Example: Hard Disk, Floppy Disk (floppy disk)

3. Random Access Method

  • Locations can be chosen randomly and can be directly addressed.
  • Data access is carried out with the help of a network Address Decoder
  • Address Decoder will generate the address of the data to be accessed
  • Fast Data Access, faster than Direct Access

Example: RAM (= random access memory)

4. Associative Access Method

  • Data access is done by “compare”, which is comparing the “content” of the data sought with the “key”, not based on the data address. As in RAM, each location has its own addressing mechanism.
  • If “matched” then the data sought is found.
  • Very Fast Data Access, Search time does not depend constantly on the location or previous access pattern.

Example: Cache Memory

Physical Characteristics of Memory

1. Volatile and Non-Volatile

Volatile: If the power goes out, then the data is lost
– This type of in-memory storage is non-permanent
Non-Volatile: If the power goes out, then the data is not lost
– This type of in-memory storage is permanent
Example: EPROM, EEPROM, Flash Memory

2. Erasable and Non-Erasable

Erasable: Data can be erased, so that it can be refilled later
1. EPROM (Erasable Programmable Read Only Memory) erased by Ultra Violet light
2. EEPROM (Electrically Erasable Programmable Read Only Memory) is electrically erased
3. FLASH Memory is erased by electricity
Non Erasable: Data can no longer be deleted, this media is only used once, if the data is incorrectly entered, it means that it must be discarded, replace the new media again
Example: ROM (Read Only Memory) , PROM (Programmable ROM)

Get to know Random Access Memory (RAM)

It is a Read/Write (R/W) memory where the contents of RAM can be updated at any time and are volatile (not permanent) and data/instructions are used during processing.

Based on its Component Structure, RAM is divided into 2 types:
1.SRAM (Static RAM), the structure is made of Bipolar Transistor components
2.DRAM (Dynamic RAM, structure made of Capacitor components)

SRAM (Static RAM):

1.Made of bipolar transistor system
2.Requires relatively large operational power
3. Does not require a Refresh circuit, due to the nature of the transistor.
4. The density of the IC chips is small (small), the capacity is small
5. The price per byte is relatively more expensive
6.Very high Data Access Speed
7.Efficient for small systems and systems that require high processing speed.

DRAM (Dynamic RAM):

1.The structure is built from Capacitor components
2.Requires relatively small operational power
3. The density of IC chips is large, so the capacity is very large
4.Requires a series to “Refresh Cycle”
5.Cheaper price
6.Efficient for large systems
7. Data access speed is relatively slow compared to SRAM

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