Jun 3, 2018
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RAM & ROM Definition – RAM & ROM Explained Difference

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What is RAM and ROM  – RAM & ROM Explained Difference

RAM & ROM Function, What are those types of memory and difference between them
RAM (Random Access Memory) is primary memory of a computer. Is a temporary workspace, where CPU can execute and process the instructions. On the other hand ROM (Read Only Memory) is another type of memory which only can be read and is used to store information necessary to boot up the computer.

RAM & ROM Differences Explained
In next lines we’ll explain the principal differences between those two memories.


can serves like a temporary workspace of CPU
is a write and read memory
data erased after computer is turned off (volatile)

used to store information necessary to boot up the PC and firmware for components
is a read only memory
data kept after the computer is turned off (non-volatile)

DRAM (DynamicRAM) is common type of memory used for our computers
SDRAM (Synchronous DRAM) the last vesion of DRAM
DDR RAM (Double Data Rate RAM) offers double faster speeds than SDRAM. There are 4 generations: DDR 1, 2, 3 and 4
SRAM (StaticRAM) faster than DRAM and used for high-speed register and caches… What is RAM and ROM

PROM (Programmable ROM) can be programmed only one time via a special device called PROM programmer at high voltages
EPROM (Erasable PROM) can be erased by exposure to strong ultraviolet light (like 10 mins) and is programmed at higher voltages than PROM
EEPROM (Electrically EPROM) can be electrically erased now and is written at slower speed (milliseconds per bit) than writting on memory module (nanoseconds per bit)

More RAM Characteristics
Speed is an important mean to measure the performance. There are 2 indicators that say the speed of a memory module: clock speed and transfer rate. For example a DDR 4 – 2133 PC-17000 RAM memory will have clock speed set at 2133 MHz and a transfer rate of 17 ,000 MB/s.

Latency or CAS Latency refers to the time it takes for a memory module to returns the solicited data to the CPU. So the lower latency will be another criteria of performance.

Voltage indicates how much power draw from the motherboard in order to operate properly. For example a DDR4 memory module draw 1,2 V in order to function. Lower voltage is an advantage because the heat generated is as well lower.

Pins is another characteristic and is indicating the number of connections it has to the motherboard. Higher number of pins will influence the transfer rate growing. The compatibility of memory with different number of pins is dictated by motherboard configuration and CPU speed.

Capacity is not the last criteria of performance but I put it like that because is well-know by almost all people with different types of devices. It refers to amount of data which can be written on a single memory module. What is RAM and ROM

DDR Performances
Because all known devices that require memory to function use DDR generations, I’ll present you the performances of each generations.

DDR 1:

capacity: 1 GB max per module
clock speed: 200 MHz to 400 MHz
Volts: 2,5 V
Pins: 184
DDR 2:

capacity: 4 GB max per module
clock speed: 400 MHz to 1066 MHz
Volts: 1,8 V
Pins: 240
DDR 3:

capacity: 8 GB max per module
clock speed: 1066 MHz to 2133 MHz
Volts: 1,5 V
Pins: 240
DDR 4:

capacity: 8 GB max per module
clock speed: 2133 MHz to 3200 MHz
Volts: 1,2 V
Pins: 240

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