Random access memory (RAM) is a type of computer memory that can be read and changed in any order, typically used to store working data and machine code. A random access memory device allows data items to be read or written at approximately the same time regardless of the physical location of the data within the memory. In contrast, other direct access data storage media such as hard disks, CD-RWs, DVD-RWs, and older magnetic tapes and memory drums, the time required to read and write data items depends on their physical location. The reason for mechanical limitations such as media rotation speed is significantly different. RAM contains multiplexing circuits, to connect data lines to addressable memory for read or write input. Usually more than one bit of storage can be accessed by the same address, and RAM devices often have multiple data lines and are said to be “8-bit” or “16-bit” devices, etc.
RAM contains multiplexing circuits, to connect data lines to addressable memory for read or write input. Usually more than one bit of storage can be accessed by the same address, and RAM devices often have multiple data lines and are said to be “8-bit” or “16-bit” devices, etc.
In today’s technology, RAM is in the form of integrated circuit (IC) chips with MOS (metal-oxide-semiconductor) memory cells. RAM is commonly associated with volatile types of memory (such as dynamic random access memory (DRAM) modules that lose stored information when power is lost), although non-volatile RAM has also been developed. Other types of non-volatile memory There are some that allow random access for read operations, but either do not allow write activity or have other limitations.These include ROM types and a type of flash memory called NOR-Flash
Types of RAM:
The two most commonly used forms of RAM are static RAM (SRAM) and dynamic RAM (DRAM). In SRAM, some data is stored using a six-transistor memory cell mode, usually using six MOSFETs (metal-oxide semiconductor field-effect transistors). This form of RAM is more expensive to manufacture, but is generally faster and requires less dynamic energy than DRAM. In modern computers, SRAM is often used as processor cache.
DRAM stores a bit of data using a pair of transistors and capacitors (a MOSFET and a MOS capacitor, respectively), which together form a DRAM cell. The capacitor has a high or low charge (1 or 0, respectively), and the transistor acts as a switch that allows the on-chip control circuit to read or change the capacitor’s state of charge.
Because this form of memory costs less to produce than static RAM, it is the dominant form of computer memory used in modern computers
The difference between RAM and RAM Static and dynamic RAM are considered volatile because their state is lost or reset when the power is removed from the system. In contrast, read-only memory (ROM) stores data by permanently turning selected transistors on or off, so the memory cannot be changed. Writable types of ROM (such as EEPROM and flash memory) share the characteristics of ROM and RAM, enabling data to persist without power and to be updated without the need for special equipment
These stable forms of semiconductor ROM include USB flash drives, memory cards for cameras and portable devices, and solid state drives. ECC memory (which can be SRAM or DRAM) contains special circuitry to detect and/or correct random errors (memory errors) in stored data, using parity bits or error correction codes. In general, the term RAM refers only to solid state memory devices (DRAM or SRAM) and specifically to main memory in most computers. In optical storage, the term DVD-RAM is somewhat of a misnomer because, unlike CD-RW or DVD-RW, it does not need to be erased before reuse. However, a DVD-RAM is almost like a hard disk, if somewhat slower
History and evolution of Rome
Early computers used main memory functions from relays, mechanical counters, or delay lines. Ultrasonic delay lines were serial devices that could only output data in written order. This memory can be developed at relatively low cost, but efficient retrieval of memory items requires physical knowledge to optimize speed. The first practical form of random access memory and the history of RAM was the Williams tube, which began in 1947. This data was stored in the form of spots of electrical charge on the surface of the cathode ray tube. Because the electron beam of the CRT could read and write the spots in the tube in any order, the memory was random access. The capacity of the Williams tube was a few hundred to about a thousand bits, but it was much smaller, faster, and more energy efficient than using separate vacuum tube latches
The Williams tube, developed at the University of Manchester in England, provided the medium on which the first electronically stored program was run on the Manchester Child computer, which first ran a program on June 21, 1948. In fact, rather than the Williams tube memory being designed for the child, the child was a test bed to demonstrate the reliability of the memory.
The evolution of Rome Magnetic core memory was invented in 1947 and evolved into RAM by the mid-1970s. Relying on a series of magnetic rings, it became a widespread form of random access memory. By changing the magnetic sense of each loop, data can be stored with one bit stored per loop. Since each loop had a combination of address
wires to select and read or write, access to any memory location in any sequence was possible.
Magnetic core memory was the standard form of computer memory system until it was replaced in the early 1970s by solid-state MOS (metal-oxide-silicon) semiconductor memory in integrated circuits (ICs). Before the development of integrated read-only memory (ROM) circuits, permanent random access (or read-only) memory was often constructed using diode arrays driven by address decoders or specially wound core-rope memory boards. Semiconductor memory began in the 1960s with bipolar memory that used bipolar transistors. Although it improved performance, it could not compete with the lower price of magnetic memory
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