Laptop RAM-Memory Price in India – DDR3,DDR2,DDR1
The term random in RAM refers to the fact that any piece of data can be returned in a constant time, irrespective of its physical location and whether it is related to the previous piece of data. RAM helps in accessing any byte of memory without touching preceding bytes. The word RAM is synonymous with the main memory and is reserved for computer related programs.
On the other hand, read-only memory (ROM) refers to computer memory which is used to store programs that boot the computer and perform diagnostics. Most of the computers have a small amount of ROM - around a few thousand bytes.
Random access memory is volatile, i.e. it requires a steady flow of electricity to maintain its contents and as soon as the power goes off, whatever data that was in the RAM is lost. RAM is commonly known as read/write memory and ROM as read-only memory. It is the most common type of memory found in computers and also other devices like printers.
On the other hand, read-only memory (ROM) refers to computer memory which is used to store programs that boot the computer and perform diagnostics. Most of the computers have a small amount of ROM - around a few thousand bytes.
Random access memory is volatile, i.e. it requires a steady flow of electricity to maintain its contents and as soon as the power goes off, whatever data that was in the RAM is lost. RAM is commonly known as read/write memory and ROM as read-only memory. It is the most common type of memory found in computers and also other devices like printers.
History
During 1949 to 1952, the magnetic core memory was widely used as a writable random access memory. It was subsequently used in most computers, until the development of the static and dynamic integrated RAM circuits in the late 1960s and early 1970s. Before RAM, computers used delay line memory, relays and different kinds of vacuum tube arrangements to implement main memory functions, which were a few hundreds or thousands of bits. Latches built out of vacuum tube triodes and discrete transistors were used for smaller and faster memories such as registers and random access register banks. Before integrated ROM circuits were developed, random access memory was constructed using semiconductor diode matrices which were driven by address decoders.
During 1949 to 1952, the magnetic core memory was widely used as a writable random access memory. It was subsequently used in most computers, until the development of the static and dynamic integrated RAM circuits in the late 1960s and early 1970s. Before RAM, computers used delay line memory, relays and different kinds of vacuum tube arrangements to implement main memory functions, which were a few hundreds or thousands of bits. Latches built out of vacuum tube triodes and discrete transistors were used for smaller and faster memories such as registers and random access register banks. Before integrated ROM circuits were developed, random access memory was constructed using semiconductor diode matrices which were driven by address decoders.
How does RAM Works?
Like any other memory chip, RAM is made up of millions of transistors and capacitors. A transistor and a capacitor are paired to create a memory cell, which represents a single bit of data. The capacitor holds the bit information as 0 or 1 and the transistor acts as a switch which allows the control circuitry on the memory chip to read the status of the capacitor or change its state. The capacitor is like a small bucket that stores electrons. To store 1 in the memory cell, the bucket is filled with electrons, and to store 0 it is emptied. The problem with the capacitor's bucket is that it leaks and within few milliseconds the full bucket becomes empty. Therefore, either the CPU or the memory controller has to recharge all capacitors holding 1 before they discharge. For this, the memory controller reads the memory and then writes it right back. This refresh operation occurs automatically nearly thousands of times per second.
Like any other memory chip, RAM is made up of millions of transistors and capacitors. A transistor and a capacitor are paired to create a memory cell, which represents a single bit of data. The capacitor holds the bit information as 0 or 1 and the transistor acts as a switch which allows the control circuitry on the memory chip to read the status of the capacitor or change its state. The capacitor is like a small bucket that stores electrons. To store 1 in the memory cell, the bucket is filled with electrons, and to store 0 it is emptied. The problem with the capacitor's bucket is that it leaks and within few milliseconds the full bucket becomes empty. Therefore, either the CPU or the memory controller has to recharge all capacitors holding 1 before they discharge. For this, the memory controller reads the memory and then writes it right back. This refresh operation occurs automatically nearly thousands of times per second.
Types of RAM
The following are some common types of RAM:
- SRAM: Static random access memory uses multiple transistors, typically four to six, for each memory cell but doesn't have a capacitor in each cell. It is used primarily for cache.
- DRAM: Dynamic random access memory has memory cells with a paired transistor andcapacitor requiring constant refreshing.
- FPM DRAM: Fast page mode dynamic random access memory was the original form of DRAM. It waits through the entire process of locating a bit of data by column and row and then reading the bit before it starts on the next bit. Maximum transfer rate to L2 cache is approximately 176 MBps.
- EDO DRAM: Extended data-out dynamic random access memory does not wait for all of the processing of the first bit before continuing to the next one. As soon as the address of the first bit is located, EDO DRAM begins looking for the next bit. It is about five percent faster than FPM. Maximum transfer rate to L2 cache is approximately 264 MBps.
- SDRAM: Synchronous dynamic random access memory takes advantage of the burst mode concept to greatly improve performance. It does this by staying on the row containing the requested bit and moving rapidly through the columns, reading each bit as it goes. The idea is that most of the time the data needed by the CPU will be in sequence. SDRAM is about five percent faster than EDO RAM and is the most common form in desktops today. Maximum transfer rate to L2 cache is approximately 528 MBps.
- DDR SDRAM: Double data rate synchronous dynamic RAM is just like SDRAM except that is has higher bandwidth, meaning greater speed. Maximum transfer rate to L2 cache is approximately 1,064 MBps (for DDR SDRAM 133 MHZ).
- RDRAM: Rambus dynamic random access memory is a radical departure from the previous DRAM architecture. Designed by Rambus, RDRAM uses a Rambus in-line memory module (RIMM), which is similar in size and pin configuration to a standard DIMM. What makes RDRAM so different is its use of a special high-speed data bus called the Rambus channel. RDRAM memory chips work in parallel to achieve a data rate of 800 MHz, or 1,600 MBps. Since they operate at such high speeds, they generate much more heat than other types of chips. To help dissipate the excess heat Rambus chips are fitted with a heat spreader, which looks like a long thin wafer. Just like there are smaller versions of DIMMs, there are also SO-RIMMs, designed for notebook computers.
- Credit Card Memory: Credit card memory is a proprietary self-contained DRAM memory module that plugs into a special slot for use in notebook computers.
- PCMCIA Memory Card: Another self-contained DRAM module for notebooks, cards of this type are not proprietary and should work with any notebook computer whose system bus matches the memory card's configuration.
- CMOS RAM: CMOS RAM is a term for the small amount of memory used by your computer and some other devices to remember things like hard disk settings -- see Why does my computer need a battery? for details. This memory uses a small battery to provide it with the power it needs to maintain the memory contents.
- VRAM: VideoRAM, also known as multiport dynamic random access memory(MPDRAM), is a type of RAM used specifically for video adapters or 3-D accelerators. The "multiport" part comes from the fact that VRAM normally has two independent access ports instead of one, allowing the CPU and graphics processor to access the RAM simultaneously. VRAM is located on the graphics card and comes in a variety of formats, many of which are proprietary. The amount of VRAM is a determining factor in the resolutionand color depth of the display. VRAM is also used to hold graphics-specific information such as 3-D geometry data and texture maps. True multiport VRAM tends to be expensive, so today, many graphics cards use SGRAM (synchronous graphics RAM) instead. Performance is nearly the same, but SGRAM is cheaper.
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