RANDOM ACCESS MEMORY

RANDOM ACCESS MEMORY

What is internal memory and how is it different from external memory?

Internal memory, often referred to as "main or primary memory," stores small quantities of data and can be accessed rapidly while the computer is functioning.

External memory, sometimes known as "secondary memory," is a type of storage device capable of retaining data over time. These devices can be either built-in or detachable, such as hard disk drives (HDDs), solid state drives (SSDs), USB flash drives, and CDs.

Types of Internal Memory

The two main categories of internal memory are ROM and RAM.

• Read-Only Memory (ROM): ROM is non-volatile, meaning it retains data even without power. Its primary purpose is to boot up or start a computer.
• Random-Access Memory (RAM): RAM is used by the computer once the operating system is loaded, serving as temporary data storage while the central processing unit (CPU) performs tasks. More RAM allows the CPU to access data quickly without relying on slower external memory, resulting in faster computer performance. However, RAM is volatile, meaning it loses data when power is off.

Types of RAM

·         Dynamic RAM (DRAM): DRAM is a common type of primary memory for computers. Each DRAM memory cell includes a transistor and a capacitor, with the capacitor storing a data bit. Due to slight leakage from transistors, capacitors discharge over time, requiring DRAM to be refreshed with a new electrical charge every few milliseconds to maintain data.

·         Static RAM (SRAM): SRAM consists of four to six transistors and retains data as long as the machine is powered on, unlike DRAM, which needs constant refreshing. Although SRAM is faster, it is also more expensive, making DRAM the more prevalent type of memory in computer systems.

Common Types of RAM

·         Synchronous DRAM (SDRAM): SDRAM synchronizes the memory speed with the CPU clock speed, allowing the memory controller to determine the exact clock cycle when requested data will be available. This enables the CPU to execute more instructions simultaneously. Typical SDRAM can transfer data at up to 133 MHz.

·         Rambus DRAM (RDRAM): Named after the company Rambus, RDRAM was popular for graphics cards and video game consoles in the early 2000s, offering transmission rates of up to 1 GHz.

·         Double Data Rate SDRAM (DDR SDRAM): DDR SDRAM uses "double pumping" to transfer data on both the rising and falling edges of the clock signal, effectively doubling the bandwidth without increasing the clock frequency. Successive generations—DDR2, DDR3, and DDR4—offer higher transfer rates and faster performance, with DDR4 modules capable of speeds like 2133, 2400, 2666, and even 3200 MT/s. Note that these modules are not backward-compatible despite following the same principles.