Random Access Memories

Random access memory (RAM) allows a computer to store and retrieve data instantly anywhere in its storage system (as opposed to disc memory which must wait for the disc to rotate to where the desired information is stored). The advent of very large quantities of very fast RAM has made today s personal computers possible. 

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A typical transputer architecture. The transputer (sometimes referred to as a computer on a chip) has four input/output links (0, 1, 2, 3) to other transputers, a channel for inputting/requesting data (event link), some built-in random-access memory, an interface to the main operating system (clock, boot, etc.), and an external memory interface. Internal communication is via a bus. 

The memory units within the computer — known as random access memory (RAM) — must be capable of change as needed to run software programs. 

Ranceite Rancidity Rancimat system Random access memory Random copolymer Random copolymers... 

Main memories almost exclusively consist of semiconductors on a siUcon basis in complementary metal oxide semiconductor technology (CMOS). The most important types are the pure read only memory (ROM) and the write/read memory (RAM = random access memory), which is available as S-RAM (static RAM) or as D-RAM (dynamic RAM). 

Today, dynamic random-access memories (DRAMs) are transistor/capacitor-based semiconductor devices, with access times measured in nanoseconds and very low costs. Core memories were made of magnetic rings not less than a millimetre in diameter, so that a megabyte of memory would have occupied square metres, while a corresponding DRAM would occupy a few square millimetres. Another version of a DRAM is the read-only memory (ROM), essential for the operation of any computer, and unalterable from the day it is manufactured. We see that developments in magnetic memories involved dramatic reductions in cost and... 

Consider the basic probkun of how information is distributed throughout a system, and the manner in which it is retrieved. We. know that in a conventional computer, for example, information is stored in random-access memory (RAM). This means that the memory address of where the information actually exists and the information itself are uncorrelated. In order to retrieve the information, one must know its address exactly, as even the slightest error renders that information effectively unretrievable. In particular, it is in general impossible to retrieve RAM data if armed only with a partial knowledge of its address. In contrast, associative memories (sometimes also called content-addressable memories), much like the form of memory believed to be used by human brains, are such that they can be completely retrieved even when searched for with partial information,... 

Forty years ago, someone interested in owning a computer would have paid approximately 150,000 for 16 megabytes of random-access memory that would have occupied a volume the size of a small desk. Today, someone can buy eight times as much computer memory for 20 and fit the chips into their shirt pocket. The difference between then and now is due to improvements in photolithogmphy, the process by which integrated-circuit chips are made. 

FIGURE 4.1 Chemical reactions are used to achieve the fine structures seen in modern integrated circuits. This electron micrograph shows a transistor in a "cell" of a 1-mega-bit dynamic random access memory chip. The distance between features is about 1 pm. Courtesy, AT T Bell Laboratories. 

The hardware situation continued to evolve. Personal computers became ever more powerful in terms of speed and the amount of random access memory (RAM) and hard drive capacity. The price of PCs continued to fall. Clusters of PCs were built. Use of the open-source Linux operating system spread in the 1990s. Distributed processing was developed so a long calculation could be farmed out to separate machines. Massively parallel processing was tried. All these changes meant that the days of the supercomputers were numbered. 

Inductively coupled plasma reactive ion etching of Co2MnSi magnetic Aims for magnetic random access memory... 

This sequence was then repeated with a different titer composition as many times as necessary to cover the required range of amphiphile/water compositions. An MS-DOS desk-top computer with 640K of random-access memory (RAM) was used to control the calorimeter and to collect thermistor voltages at the fixed time intervals. Spread-sheet macros running on this same computer were used to make various plots, including thermistor voltage y . time and corrected heat ys time. 

One of the more important applications of ion implantation is well engineering at relatively high ion energies. For the protection of dynamic random access memories from soft errors, different structures have been proposed and employed. The conventional procedure is to use epitaxial wafers well engineering beneath the active p- and n-channels provides a less expensive alternative. 

Reed, M. A. Chen, J. Rawlett, A. M. Price, D. W. Tour, J. M. 2001. Molecular random access memory cell. Appl. Phys. Lett. 78 3735-3737. 

Computers contain read-only memory whose contents are permanent (i.e., can only be read and not written to by the user) along with random access memory that can both be read from and written to by the user. The basic computing unit is a bit (b), which stands for binary digit 8 bits comprise a byte (B). Table 3.5 illustrates calculation of computer memory bytes, i.e., the number of locations that can be addressed. 

There are two types of memory used in computers. The main memory is based on integrated circuit chips and all parts can be accessed with great rapidity and with equal ease. In mainframe computers this is known as the main store whilst in smaller computers, including microcomputers, it is called the random access memory (RAM). Some parts of RAM may be reserved for the storage of programs or data which are to be protected from change or accidental erasure. Such a reserved area of memory is called read only memory (ROM). ROM chips, sometimes called firmware, are often used in integrators and microcomputers dedicated to particular tasks. The... 

Dynamic random access memory (DRAM) silicon-based semiconductors and, 22 229, 230, 231, 250, 257, 258 vitreous silica in, 22 443 Dynamic random access memory devices, 10 3... 

Fig. 4.15 The use of etch stops to visualize defects in a dynamic random access memory (DRAM) structure for subsequent electron microscopy inspection. If a bias is applied to the silicon substrate, as shown in (a), the polysili-...

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