The term random access as applied to RAM comes from the fact that any storage location, also known as any memory address, can be accessed directly. Originally, the term Random Access Memory was used to distinguish regular core memory from offline memory.
Offline memory typically referred to magnetic tape from which a specific piece of data could only be accessed by locating the address sequentially, starting at the beginning of the tape. RAM is organized and controlled in a way that enables data to be stored and retrieved directly to and from specific locations. Other types of storage -- such as the hard drive and CD-ROM -- are also accessed directly or randomly, but the term random access isn't used to describe these other types of storage.
RAM is similar in concept to a set of boxes in which each box can hold a 0 or a 1. Each box has a unique address that is found by counting across the columns and down the rows. A set of RAM boxes is called an array , and each box is known as a cell. To find a specific cell, the RAM controller sends the column and row address down a thin electrical line etched into the chip. Each row and column in a RAM array has its own address line. Any data that's read flows back on a separate data line.
RAM is physically small and stored in microchips. It's also small in terms of the amount of data it can hold. A typical laptop computer may come with 8 gigabytes of RAM, while a hard disk can hold 10 terabytes. RAM microchips are gathered together into memory modules , which plug into slots in a computer's motherboard. A bus , or a set of electrical paths, is used to connect the motherboard slots to the processor.
A hard drive, on the other hand, stores data on the magnetized surface of what looks like a vinyl record. And, alternatively, an SSD stores data in memory chips that, unlike RAM, are nonvolatile, don't depend on having constant power and won't lose data once the power is turned off.
Having more RAM in a computer cuts down on the number of times the processor must read data from the hard disk, an operation that takes longer than reading data from RAM.
RAM access time is in nanoseconds , while storage memory access time is in milliseconds. Each DRAM cell has a charge or lack of charge held in an electrical capacitor. This data must be constantly refreshed with an electronic charge every few milliseconds to compensate for leaks from the capacitator. A transistor serves as a gate, determining whether a capacitor's value can be read or written. In SRAM, instead of a capacitor holding the charge, the transistor acts as a switch, with one position serving as 1 and the other position as 0.
Static RAM requires several transistors to retain one bit of data compared to dynamic RAM which needs only one transistor per bit. The price and speed differences mean static RAM is mainly used in small amounts as cache memory inside a computer's processor. RAM was originally asynchronous because the RAM microchips had a different clock speed than the computer's processor. This was a problem as processors became more powerful and RAM couldn't keep up with the processor's requests for data.
By synchronizing a computer's memory with the inputs from the processor, computers were able to execute tasks faster. This moved data twice in a single clock cycle, at the start and the end. However, each DDR version has been incompatible with earlier ones because, with each iteration, data is handled in larger batches. With parallel tasks, such as 2D and 3D video rendering , tight access times aren't as necessary, and GDDR can enable the higher speeds and memory bandwidth needed for GPU performance.
Similar to DDR, GDDR has gone through several generations of development, with each providing more performance and lower power consumption.
GDDR6 is the latest generation of graphics memory. A computer can run short on memory, especially when running multiple programs simultaneously.
Operating systems can compensate for physical memory shortfalls by creating virtual memory. With virtual memory, data is temporarily transferred from RAM to disk storage, and virtual address space is increased using active memory in RAM and inactive memory in an HDD to form contiguous addresses that hold an application and its data. Using virtual memory, a system can load larger programs or multiple programs running at the same time, letting each operate as if it has infinite memory without having to add more RAM.
Virtual memory is able to handle twice as many addresses as RAM. A program's instructions and data are initially stored at virtual addresses , and once the program is executed, those addresses are turned into actual memory addresses. One downside to virtual memory is that it can slow a computer because data must be mapped between the virtual and physical memory.
With physical memory alone, programs work directly from RAM. Flash memory and RAM are both comprised of solid-state chips, but they play different roles in computer systems because of differences in the way they're made, their performance specifications and cost. Flash memory is used for storage memory, while RAM is used as active memory that performs calculations on the data retrieved from storage. One significant difference between RAM and flash memory is that data must be erased from NAND flash memory in entire blocks, making it slower than RAM, where data can be erased in individual bits.
Because of its slower speed, nonvolatility and lower cost, flash is often used for storage memory in SSDs. Read-only memory, or ROM , is computer memory containing data that can only be read, not written to.
ROM contains boot-up programming that is used each time a computer is turned on. It generally can't be altered or reprogrammed. The data in ROM is nonvolatile and isn't lost when the computer power is turned off.
Research indicates that the amygdala is extremely active during emotional situations, and acts with the hippocampus and prefrontal cortex in the encoding and consolidation of emotional events. Working memory is not part of long-term memory, but is important for long-term memory to function. Working memory holds and manipulates information for a short period of time, before it is either forgotten or encoded into long-term memory.
Then, in order to remember something from long-term memory, it must be brought back into working memory. If working memory is overloaded it can affect the encoding of long-term memory. If one has a good working memory they may have a better long-term memory encoding. Minor everyday slips and lapses of memory are fairly commonplace, and may increase naturally with age, when ill, or when under stress.
Some women may experience more memory lapses following the onset of the menopause. The majority of findings about memory have been the result of studies that lesioned specific brain regions in rats or primates, but some of the most important work has been the result of accidental or inadvertent brain trauma.
The most famous case in recent memory studies is the case study of HM , who had parts of his hippocampus, parahippocampal cortices , and surrounding tissue removed in an attempt to cure his epilepsy.
His subsequent total anterograde amnesia and partial retrograde amnesia provided the first evidence for the localization of memory function, and further clarified the differences between declarative and procedural memory.
Many neurodegenerative diseases can cause memory loss. Some of the most prevalent and, as a consequence, most intensely researched include Alzheimer's disease , dementia , Huntington's disease , multiple sclerosis , Parkinson's disease , and schizophrenia. None act specifically on memory; instead, memory loss is often a casualty of generalized neuronal deterioration. Currently, these illnesses are irreversible, but research into stem cells, psychopharmacology, and genetic engineering holds much promise.
Those with Alzheimer's disease generally display symptoms such as getting momentarily lost on familiar routes, placing possessions in inappropriate locations and distortions of existing memories or completely forgetting memories. The DRM paradigm presents a list of words such as doze, pillow, bed, dream, nap, etc.
In this case the theme word would have been sleep. Alzheimer's disease patients are more likely to recall the theme word as being part of the original list than healthy adults. There is a possible link between longer encoding time and increased false memory in LTM. The patients end up relying on the gist of information instead of the specific words themselves.
This gets worse over time and eventually leads to cognitive decline, after the loss of memory. Pioglitazone may improve cognitive impairments, including memory loss and may help protect long-term and visiospatial memory from neurodegenerative disease.
Parkinson's disease patients have problems with cognitive performance; these issues resemble what is seen in frontal lobe patients and can often lead to dementia. It is thought that Parkinson's disease is caused by degradation of the dopaminergic mesocorticolimbic projection originating from the ventral tegmental area. It has also been indicated that the hippocampus plays an important role in episodic and spatial parts of LTM memory and Parkinson's disease patients have abnormal hippocampuses resulting in abnormal functioning of LTM.
L-dopa injections are often used to try to relieve Parkinson's disease symptoms as well as behavioral therapy. Schizophrenia patients have trouble with attention and executive functions which in turn affects long-term memory consolidation and retrieval.
They cannot encode or retrieve temporal information properly, which causes them to select inappropriate social behaviors. They cannot effectively use the information they possess. The prefrontal cortex, where schizophrenia patients have structural abnormalities, is involved with the temporal lobe and also affects the hippocampus, which causes their difficulty in encoding and retrieving temporal information including long-term memory.
Long-term memory, unlike short-term memory, is dependent upon the synthesis of new proteins. The production of new proteins devoted to synapse reinforcement is triggered after the release of certain signaling substances such as calcium within hippocampal neurons in the cell. In the case of hippocampal cells, this release is dependent upon the expulsion of magnesium a binding molecule that is expelled after significant and repetitive synaptic signaling.
The temporary expulsion of magnesium frees NMDA receptors to release calcium in the cell, a signal that leads to gene transcription and the construction of reinforcing proteins.
One of the newly synthesized proteins in LTP is also critical for maintaining long-term memory. Also, BDNF is important for the persistence of long-term memories. The long-term stabilization of synaptic changes is also determined by a parallel increase of pre- and postsynaptic structures such as axonal bouton , dendritic spine and postsynaptic density.
The cAMP response element-binding protein CREB is a transcription factor which is believed to be important in consolidating short-term to long-term memories, and which is believed to be downregulated in Alzheimer's disease. A couple of studies have had results that contradict the dual-store memory model. Studies showed that in spite of using distractors, there was still both a recency effect for a list of items  and a contiguity effect.
Another study revealed that how long an item spends in short-term memory is not the key determinant in its strength in long-term memory.
Instead, whether the participant actively tries to remember the item while elaborating on its meaning determines the strength of its store in long-term memory. An alternative theory is that there is only one memory store with associations among items and their contexts.
In this model, the context serves as a cue for retrieval, and the recency effect is greatly caused by the factor of context. Immediate and delayed free-recall will have the same recency effect because the relative similarity of the contexts still exist.
Also, the contiguity effect still occurs because contiguity also exists between similar contexts. From Wikipedia, the free encyclopedia. A proposed system and its control processes". The psychology of learning and motivation. Psychology of Learning and Motivation. The Quarterly Journal of Experimental Psychology. Q J Exp Psychol. Annual Review of Psychology.
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Journal of Verbal Learning and Verbal Behavior.
Long-term memory is, obviously enough, intended for storage of information over a long period of time. Despite our everyday impressions of forgetting, it seems likely that long-term memory actually decays very little over time, and can store a seemingly unlimited amount of information almost indefinitely.
Long-term memory refers to the storage of information over an extended period. If you can remember something that happened more than just a few moments ago whether it occurred just hours ago or decades earlier, then it is a long-term memory.
ROM, or read only memory, is a computer's long-term memory and is used to store data even after the computer is turned off. An example of ROM is a computer's hard drive, which is where most people choose to save documents, pictures, music and more. Long-Term Memory vs. Short-Term Memory. At the core of every computer is its capacity to remember things: sets of instructions, particular files you've created, how much memory is left, where you put your keys. Computers store all this memory in two distinct ways. The main memory bank is called the hard drive. It stores all the files you save.
One of the first signs of dementia is short-term memory loss. People who have been victims of or witnessed a traumatic event such as a violent crime or accident can also have their short-term memories affected. Short-term vs. long-term memory. Short-term memory is the information that a person is currently thinking about or is aware of. Bahrick et al. () investigated what they called very long term memory (VLTM). Nearly participants aged 17 – 74 were tested. There were various tests including: A free recall test, where participants tried to remember names of people in a graduate class. A photo recognition test, consisting of 50 eroticlesbian.ml: Saul Mcleod.