Error Checking Memory
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computer data storage that can detect and correct the most common kinds of internal data corruption. ECC memory is how does ecc memory work used in most computers where data corruption cannot be tolerated under which are two types of error correction used in ram any circumstances, such as for scientific or financial computing. Typically, ECC memory maintains a memory system immune ecc bits to single-bit errors: the data that is read from each word is always the same as the data that had been written to it, even if one or 2 error checking methods for memory more bits actually stored have been flipped to the wrong state. Most non-ECC memory cannot detect errors although some non-ECC memory with parity support allows detection but not correction. Contents 1 Problem background 2 Solutions 3 Implementations 4 Cache 5 Registered memory 6 Advantages and disadvantages 7 References 8 External links Problem background[edit] Electrical or magnetic
Checking Computer Memory
interference inside a computer system can cause a single bit of dynamic random-access memory (DRAM) to spontaneously flip to the opposite state. It was initially thought that this was mainly due to alpha particles emitted by contaminants in chip packaging material, but research has shown that the majority of one-off soft errors in DRAM chips occur as a result of background radiation, chiefly neutrons from cosmic ray secondaries, which may change the contents of one or more memory cells or interfere with the circuitry used to read or write to them.[2] Hence, the error rates increase rapidly with rising altitude; for example, compared to the sea level, the rate of neutron flux is 3.5 times higher at 1.5km and 300 times higher at 10–12km (the cruising altitude of commercial airplanes).[3] As a result, systems operating at high altitudes require special provision for reliability. As an example, the spacecraft Cassini–Huygens, launched in 1997, contains two identical flight recorders, each with 2.5gigabits of memory in the form o
citations to reliable sources. Unsourced material may be challenged and removed. (August 2008) (Learn how and when to remove this template message) In information theory and
Checking Pc Memory
coding theory with applications in computer science and telecommunication, error detection checking laptop memory and correction or error control are techniques that enable reliable delivery of digital data over unreliable communication channels. checking memory in aix Many communication channels are subject to channel noise, and thus errors may be introduced during transmission from the source to a receiver. Error detection techniques allow detecting such errors, https://en.wikipedia.org/wiki/ECC_memory while error correction enables reconstruction of the original data in many cases. Contents 1 Definitions 2 History 3 Introduction 4 Implementation 5 Error detection schemes 5.1 Repetition codes 5.2 Parity bits 5.3 Checksums 5.4 Cyclic redundancy checks (CRCs) 5.5 Cryptographic hash functions 5.6 Error-correcting codes 6 Error correction 6.1 Automatic repeat request (ARQ) 6.2 Error-correcting code 6.3 Hybrid schemes https://en.wikipedia.org/wiki/Error_detection_and_correction 7 Applications 7.1 Internet 7.2 Deep-space telecommunications 7.3 Satellite broadcasting (DVB) 7.4 Data storage 7.5 Error-correcting memory 8 See also 9 References 10 Further reading 11 External links Definitions[edit] The general definitions of the terms are as follows: Error detection is the detection of errors caused by noise or other impairments during transmission from the transmitter to the receiver. Error correction is the detection of errors and reconstruction of the original, error-free data. History[edit] The modern development of error-correcting codes in 1947 is due to Richard W. Hamming.[1] A description of Hamming's code appeared in Claude Shannon's A Mathematical Theory of Communication[2] and was quickly generalized by Marcel J. E. Golay.[3] Introduction[edit] The general idea for achieving error detection and correction is to add some redundancy (i.e., some extra data) to a message, which receivers can use to check consistency of the delivered message, and to recover data determined to be corrupted. Error-detection and correction schemes can be either systematic or non-systematic: In a systematic scheme, the transmitter sends the original data, and attac
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Parity versus non-parity In this section you learn about parity versus non-parity memory. Parity memory is a type of error-checking memory, which is memory that verifies the information stored in memory is what is actually read from memory at a later time. Non-parity memory is simply memory that does not perform any kind of error checking to ensure that the data written to memory is what is actually read when it is retrieved. Let's look at how parity memory works! There are two types of parity memory: odd parity and even parity. Both parity methods function the same way but differ in the sense of whether they look for an odd number of bits or an even number of bits. This discussion uses odd parity as the example. With parity memory, for every byte (8 bits) of data written to memory, there is an additional 9th bit known as the parity bit. When storing information to memory, the number of the enabled data bits (bits set to 1) written to memory are added up. With odd parity, if an even number of data bits are enabled, the parity bit is set to 1 (enabled) so that there is an odd number of enabled bits in total written to memory. If the result of all the enabled data bits is odd, the parity bit is set to 0 (disabled) so that the odd number of enabled bits is retained. After the parity bit has been set, the byte of data and the parity bit are written to memory. Note that even parity works the same way, only it looks for an even number of enabled bits; if the number of enabled bits is odd, then the parity bit is enabled. When the CPU requests data from memory, the data byte is retrieved along with the parity bit that was generated when the byte of information was stored in memory. The system looks at the data byte and calculates whether the parity bit stored in memory should be set to 1 or 0. It then compares the answer it has just generated with the value of the parity bit stored in memory. If the two match, the integrity of the information in memory is considered okay, the parity bit is stripped from the data byte, and the data is delivered to the CPU. If the two differ, you have a parity error, meaning that there is a problem with the integrity of the data stored in memory. Note that parity memory cannot correct the error; it just reports that an error exists. ECC memory Error-checking and correction (ECC) memory is memory that can detect data integrity problems the way that parity memory can, the difference being that ECC memory can recover from the error and attempt t