Types of Memory

Types of Memory

1. RAM

   • RAM (Random Access Memory) is a type of memory that is volatile, meaning it loses it's content stored when the system is turned off. It needs to be refreshed during the time between the computer is turned on and off to keep it's contents.
   • RAM is used to retain the contents, such as programs and process that are being used by the computer after the start up. 
   • SRAM (Static RAM)
     • SRAM (Static Random Access Memory) is RAM that is made from tiny bi-polar electric cells that don't require to be constantly refreshed to keep it's contents (SRAM is still volatile however).
     • Even though this makes SRAM much faster, it also requires much more power meaning it is often only used as cache memory and random access memory digital to analog (RAMDAC) used in video cards.
   • DRAM (Dynamic RAM)
     • DRAM (Dynamic Random Access Memory) is the most typical type of RAM. It uses tiny capacitors and transistors to holds its contents that is then constantly refreshed using an electric current.
     • Synchronous
       • SDRAM (Synchronous DRAM) is the DRAM used in all motherboard as it runs synchronised with the system buses and waits for clock signals.
     • Double Datarate
       • Double Datarate (DDR) is the most common type of DRAM that is used in mother systems. DDR uses both phases of the clock cycle to increase transfer speed. Types of DDR have been DDR, DDR2, DDR3 and DDR4
   • RAMDAC
     • RAMDAC (RAM Digital-Analog Converter) which converts digital images into analog data needed to be displayed on a computer. It is made of a small SRAM that contains a colour table and three digital-analog converter that converts the data and sends them to the three display colour generators (red, blue and green).
   • Cache
     • Cache memory is memory placed in-between RAM and the CPU which keeps and retains regularly referenced data. Before checking RAM the CPU checks cache to see if a copy is saved there. The closer the cache is located to the processor, the faster it can be accessed. Sometimes it can be located on the processor. 

2. ROM

   • ROM (Read-Only Memory) is a non-volatile form of  memory, meaning  that the memory doesn't lose it's contents when the computer is switched off. ROM is made up of using fuses, some are blown and other aren't to represent 1's or 0's. This makes ROM slower than RAM
   • ROM is  used to start up the computer. A primary example of ROM is the BIOS (Basic Input-Output System) which preforms  POST (Power On-Self Test), load the OS through the Bootstrap Loader, load Input -Output devices and configure hardware setting using CMOS setup.
   • PROM
     • PROM (Programmable ROM) is ROM that is created from blank, with high setup costs and has the program burned into it later at much cheaper rates.
   • EPROM
     • EPROM (Erasable Programmable ROM) IS ROM that can be erased using UV light then reprogrammed using a PROM burner. 
   • EEPROM
     • EEPROM (Electrical Erasable Programmable ROM) is the same as EPROM but an electrical current is used to erase the the program not a UV light.