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Concept: Is read-only memory. Do not lose data when power is lost. ROM memory is used to produce chips with integrated CMOS

BIOS program

Characteristics of the ROM BIOS BIOS ROM containing the software configuration and system

diagnostics, and routine input / output low level that DOS uses. These programs are encoded in ROM and is called firmware. An important feature of the ROM BIOS is detecting new

hardware in the computer and reconfigure the operating system as device driver.


ROM (Read Only Memory)

ROM Types

PROM (Programmable Read Only Memory) Type of ROM that information is only installed once. The CD can be called PROM.

EPROM (Erasable Programmable ROM): Type of ROM that can erase and rewrite it. "CD-Erasable" can be called EPROM.

EEPROM (Electronic Erasable Programmable ROM): It form enhence of EPROM, a difference compared to the

EPROM is able to write and remove the information again and again by software rather than hardware.

Example: "CD-Rewritable". Application specific EEPROM is "flash BIOS". ROM is the

type of information can install or upgrade software.


RAM – Random Access Memory

Concept: RAM (Random Access Memory) to store in direct service

programs for the processing of the CPU. The RAM is only temporary data storage and data will be

deleted when power off.

RAM operation Enter your information will be stored in RAM, then CPU will

retrieve data from RAM to handle.

Types of RAM SRAM (Static RAM): SRAM is a type of RAM data storage

without the need to update regularly (static). DRAM (Dynamic RAM)

DRAM is a type of RAM should regularly update the data (high refresh rate).


SRAM – Static RAM

Characteristics: Allow faster access than DRAM The memory chips are made of the transistors (switches) and

capacitors. Transistor SRAM can hold state power. SRAM is more expensive than DRAM Ex: L1, L2, L3 cache.


DRAM - Dynamic RAM

Characteristics: Dynamic RAM is mounted on the modules: DIMM , SIMM or

RIMM. Be plugged directly into the motherboard

The most popular form factors: SIMM DIMM RIMM SoDIMM


SIMM - Single In-Line Memory Module


DIMM - Dual Inline Memory Module

DIMMs are 64-bit memory modules The DIMM RAM family: SDRAM, DDR, and DDR2.

SDRAM: (Synchronous DRAM) With 84 pins per side, this makes 168 independent pins on each standard .SDRAM module and two keys notches.


DDR SDRAM (Double-Data Rate SDRAM) memory has a total of 184 pins and a single keying notch.


DDR2 has a total of 240 pins, one keying notch, and an aluminum cover for both sides


RIMM - Rambus DRAM

A RIMM is a custom memory module that varies in physical specification based on whether it is a 16-bit or 32-bit module.

The 16-bit modules have 184 pins and two keying notches.

The 32-bit modules have 232 pins and only one keying notch.


SoDIMM - Small Outline DIMM

Memory in use for notebook and other computers that require much smaller components don’t use standard RAM packages like the SIMM or the DIMM.

Including: 144-pin EDO, 144-pin SDRAM and 200-pin DDR/DDR2.


Structure Of Memory Chip


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RAS - Row Address Strobe CAS - Column Address Strobe Address Bus: signal address between RAS and CAS. Data Bus is the data path between memory controller and

memory chips. Column Address Decoder. Row Address Decoder. Row(column) addr latch. Write Enable: check section to read - write the memory cell.

The specifications of the RAM

Bus speed: measured in MHz, is that the volume of data in RAM can be transmitted to the CPU once handled.

Retrieve data speed: measured in billionths of a second (nanosecond), the time interval between two data acquisition of RAM

Capacity: measured in MB (megabytes), showing a maximum level of stocks of RAM when the RAM data completely empty.

RAM ECC (Error Correction Code): This is a technique to test and debug in case of a bit of memory was incorrect value data during transport.


Bandwidth of RAM

Single Channel BandWidth = Bus Speed *8 Ex: DDR-SDRAM 400 MHZ

• BandWidth = 400 *8 = 3200MB/s, is called PC3200.

Dual Channel BandWidth = Bus Speed * 2*8 = Bus Speed * 16 Ex: DDR 400 MHz => Bandwidth = 400*16 = 6400 Is called 6400.


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