RAM:
Random Access Memory.
Invention:
In 1968, by Robert Dennard.
How it is made:
Millions of transistors and capacitors.
Transistor:
Semiconductor device used to amplify.
Capacitor:
Stores electric charge.
What does RAM store:
Load a program or open a document it is read from your hard drive and stored in RAM.
Why RAM is needed:
Quickly reached by computer processor as long as computer is running.
Function of RAM:
Find specific information quickly.
Is RAM temporary or permanent storage:
Temporary storage, Once your computer turns off data in RAM is lost.
Types:
SRAM:
Static random access memory (S-RAM).
Expensive.
Faster.
Retains data bits in its memory as long as power is being supplied.
DRAM:
Dynamic random access memory.
Less cost.
Slower.
Capacitor can hold 0 (or) 1.
Can access one block of data at a time.
FPM DRAM:
Fast page mode dynamic random access memory.
EDO RAM:
Extended data out dynamic random access memory.
Faster than conventional DRAM.
Can also fetch the next block of memory at the same time.
Synchronous dynamic random access memory.
Number of instructions that processor can perform in given time.
Double data rate synchronous dynamic ram.
Supports data transfers on both edges of clock cycle.
Rambus dynamic random access memory.
Designed to transfer data at faster rates.
Examples:
Mobile phones.
Hard disks.
CD-drives.
Advantages:
Fast means storage will be fast.
Power efficient means less power battery will stay long time.
Disadvantages:
Volatile.
Volatile:
Power is turned off data on RAM is completely erased.
Read Only Memory.
Invention:
In 1980, by Intel.
Why ROM is needed:
Retains its memory even computer is turned off.
Is ROM temporary or permanent storage:
ROM is permanent storage and it will not be erased off during the power off.
Types of ROM:
PROM:
Wen Tsing Chow in 1956.
Programmable ROM (or) Field programable Read Only Memory.
Information written is permanent cannot be erased or deleted.
EPROM:
Erasable Programable Read Only Memory.
Memory can be erased by exposing to strong ultraviolet light source designed and reused.
EEPROM:
Electrically Erasable Programable Read Only Memory.
Stores small amount of data but allow individual byte to be erased and reprogrammed.
Examples:
Video games.
BIOS.
Advantages:
Non volatile means store data for long time.
Disadvantages:
It cannot remove data store permanently.
Differences between RAM and ROM:
| RAM | ROM |
|---|---|
| Random Access Memory | Read Only Memory |
| RAM is a volatile memory, so once the voltage supply is lost data is removed from the memory | ROM is a non volatile memory, it is not erasable data remains in storage until hardware is damaged |
| RAM is a temporary memory | ROM is a permanent memory |
| Access time is very short in RAM | Access time is long in ROM |
| RAM is easily accessed by the processor | ROM cant be directly accessed by the processor |
| RAM is a form of chip | ROM is generally optical drivers made of magnetic tapes |
| RAM is expensive | ROM is cheaper compared to RAM |
| RAM is a primary memory | ROM is a secondary memory |
| Static RAM and dynamic RAM are types of RAM | PROM, EPROM, EEPROM are types of ROM |