Edited by Ross Stone
- Article ID: 38
Learn about laptop memory
Random Access Memory (RAM) is known as the working space in a computer. It is accessed by the Central Processing Unit (CPU) to temporarily read and write data and programs, this can be done directly and randomly. The more memory a computer has the faster it will work because more memory limits the number of times the Central Processing Unit (CPU) reads data from the hard disk. Random Access Memory is volatile, meaning that once the computer is turned off, data in RAM is lost forever. They are many different types of RAM; one type of RAM will not work with another RAM type because of physical differences.
RAM is measured by the use of terms such as bytes (B), kilobytes (KB), megabytes (MB), and gigabytes (GB) the latter being the highest.
The earliest form of writable random access memory was the magnetic core memory developed from the 1940s to the1950s. This memory type was made from metallic wirings aligned through magnetic rings, data was stored using polarity. This type of memory was used by most computers until the 1970s when the semiconductor technology was incorporated. Intel was the first company to develop, manufacture and market the semiconductor core memory.
Types of RAM
Static Random Access Memory (SRAM): this type of memory is much faster than DRAM because there’s no need to refresh, data can be accessed in 10 nanoseconds. A SRAM cell is made up of 6 transistors which are used to store a 0 or 1. The transistor stores data permanently within the transistor as long as electric flows. SRAM is much more efficient and expensive than DRAM; it is mainly used as CPU cache memory and hard drive disk cache.
Dynamic Random Access Memory DRAM: This type of memory is used by most if not all modern computers. Each bit of information is stored in a cell which consists of a transistor and a capacitor. Capacitors lose electrons very fast hence the need for the cells to refresh after a few milliseconds this is why it is called Dynamic RAM. In order to refresh DRAM, the memory controller will read and then write back the information. DRAM is much cheaper than SRAM because of how it is densely structured.
There are many different types of DRAM, which makes it possible to install different DRAM on your motherboard if the motherboard supports this but performance of the computer may be reduced as a result.
Synchronous Dynamic Random Access Memory SDRAM takes advantage of the burst technology which helps to increase performance greatly, this is accomplished by ensuring that data is kept on the same row and moving this information rapidly across the columns, each bit is read during data processing. SDRAM consists of 168 pins and two connector notches, this is to prevent the use of SDRAM on a DDR SDRAM motherboard.
Double Data Rate Synchronous Dynamic RAM DDR SDRAM operates at a much faster speed when compared to SDRAM. DDR Memory uses a 184 pin DIMM module for desktops and 200 pin SODIM for laptops, it has a single notch at the connector.
Rambus Dynamic Random Access Memory RDRAM uses a rambus channel that works in parallel for high speed data transfer rate of 800 Megahertz (Mhz). Since they work at such high speeds they generate a lot of heat when compared to other types of chips. To help dispel the excess heat RDRAM chips are fitted with a heat spreader.
The memory hierarchical structure is a result of physical and economic limitations. Faster memory modules are more likely to be less dense and much more costly than slower modules. For example, a DRAM chip is 16 times denser than a SRAM chip, but the DRAM is 8 to 16 times slower than SRAM. Access time and density are both increased when reading from secondary disk storage. Therefore, systems designers make cost performance decisions by using SRAM memory for processor cache and DRAM for slower and larger main memory and virtual disk memory. The basic laws of physics (the speed of light) necessitates that faster modules are situated nearer to the processor. Therefore the typical memory hierarchy consists of on-chip cache, registers, off-chip cache, virtual memory, and main memory.
Uses of RAM
In addition to being used as working space and temporary storage, RAM is also used in many other ways they are as follows:
Virtual Memory: Modern operating systems use virtual memory as a means of extending RAM physical capacity. A portion of the hard disk space is reserved as a paging file; the total system memory is equal to the combination of physical and virtual memory.
RAM disk: this is a section of a RAM that is used by software programs to access data much faster; the RAM disk acts as a high speed hard drive.