A Parity Error
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in random access memory, and the subsequent comparison of the stored and the computed parity to detect whether a data error has occurred. The parity bit was originally stored in additional individual memory memory parity error chips; with the introduction of plug-in DIMM, SIMM, etc. modules, they became available in
Parity Error Blue Screen
non-parity and parity (with an extra bit per byte, storing 9 bits for every 8 bits of actual data) versions. Contents 1
Parity Error System Halted
History 2 Memory errors 3 Error correction 3.1 ECC type RAM 4 See also 5 References History[edit] Early computers sometimes required the use of parity RAM, and parity-checking could not be disabled. A parity error
Parity Bit
typically caused the machine to halt, with loss of unsaved data; this is usually a better option than saving corrupt data. Logic parity RAM, also known as fake parity RAM, is non-parity RAM that can be used in computers that require parity RAM. Logic parity RAM recalculates an always-valid parity bit each time a byte is read from memory, instead of storing the parity bit when the memory is written to; the nmi parity check memory parity error calculated parity bit, which will not reveal if the data has been corrupted (hence the name "fake parity"), is presented to the parity-checking logic. It is a means of using cheaper 8-bit RAM in a system designed to use only 9-bit parity RAM. Memory errors[edit] In the 1970s-80s, RAM reliability was often less-than-perfect; in particular, the 4116 DRAMs which were an industry standard from 1975 to 1983 had a considerable failure rate as they used triple voltages (-5, +5, and +12) which resulted in high operating temperatures. By the mid-1980s, these had given way to single voltage DRAM such as the 4164 and 41256 with the result of improved reliability. However, RAM did not achieve modern standards of reliability until the 1990s. Since then errors have become less visible as simple parity RAM has fallen out of use; either they are invisible as they are not detected, or they are corrected invisibly with ECC RAM. Modern RAM is believed, with much justification, to be reliable, and error-detecting RAM has largely fallen out of use for non-critical applications. By the mid-1990s, most DRAM had dropped parity checking as manufacturers felt confident that it was no longer necessary. Some machines that support parity or ECC allow checking to be enabled or disabled in
in random access memory, and the subsequent comparison of the stored and the computed parity to detect whether a data error has occurred. The parity bit was originally stored in additional individual memory chips; with the introduction of plug-in DIMM, SIMM, etc. parity error wiki modules, they became available in non-parity and parity (with an extra bit per byte, storing 9 parity error 4x4 bits for every 8 bits of actual data) versions. Contents 1 History 2 Memory errors 3 Error correction 3.1 ECC type RAM 4 See parity error rubik cube also 5 References History[edit] Early computers sometimes required the use of parity RAM, and parity-checking could not be disabled. A parity error typically caused the machine to halt, with loss of unsaved data; this is usually a better option than https://en.wikipedia.org/wiki/RAM_parity saving corrupt data. Logic parity RAM, also known as fake parity RAM, is non-parity RAM that can be used in computers that require parity RAM. Logic parity RAM recalculates an always-valid parity bit each time a byte is read from memory, instead of storing the parity bit when the memory is written to; the calculated parity bit, which will not reveal if the data has been corrupted (hence the name "fake parity"), is presented to the parity-checking logic. It is a https://en.wikipedia.org/wiki/RAM_parity means of using cheaper 8-bit RAM in a system designed to use only 9-bit parity RAM. Memory errors[edit] In the 1970s-80s, RAM reliability was often less-than-perfect; in particular, the 4116 DRAMs which were an industry standard from 1975 to 1983 had a considerable failure rate as they used triple voltages (-5, +5, and +12) which resulted in high operating temperatures. By the mid-1980s, these had given way to single voltage DRAM such as the 4164 and 41256 with the result of improved reliability. However, RAM did not achieve modern standards of reliability until the 1990s. Since then errors have become less visible as simple parity RAM has fallen out of use; either they are invisible as they are not detected, or they are corrected invisibly with ECC RAM. Modern RAM is believed, with much justification, to be reliable, and error-detecting RAM has largely fallen out of use for non-critical applications. By the mid-1990s, most DRAM had dropped parity checking as manufacturers felt confident that it was no longer necessary. Some machines that support parity or ECC allow checking to be enabled or disabled in the BIOS, permitting cheaper non-parity RAM to be used. If parity RAM is used the chipset will usually use it to implement error correction, rather than halting the machine on a single-bit parity error. However, as discussed in the article on ECC memory, errors, while not everyday events, are not negligibly infrequent. Even in the
Catalyst 6500 Series SwitchesTroubleshoot and AlertsTroubleshooting TechNotes Parity Errors Troubleshooting Guide Download Print Available Languages Download Options PDF (259.4 KB) View with Adobe Reader on a variety of devices http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/116135-trouble-6500-parity-00.html Updated:Jul 15, 2013 Document ID:116135 Document ID: 116135 Updated: Jul 15, 2013 Contributed by Shawn Wargo, Cisco Engineering. Download PDF Print Feedback Related ProductsCisco Catalyst 6500 Series Switches ContentsIntroductionBackgroundSoft ErrorsHard ErrorsCommon http://www.webopedia.com/TERM/P/parity_checking.html Error MessagesProcessorRAMASICLatest AdvancementsProcessorRAMASICSoftwareMSFC IBC Reset6700 Series 'Single-Bit Parity Error' ResetRecommendationsSoft Errors (SEU)Environmental AuditLatest Firmware (Rommon)Thumb ScrewsHard Errors (Malfunction)Hardware (MTBF and EOL) AuditHardware DiagnosticsRelated Cisco Support Community DiscussionsIntroductionThis document describes soft and hard parity parity error errors, explains common error messages, and recommends methods that help you avoid or minimize parity errors. Recent improvements in hardware and software design reduce parity problems as well. BackgroundWhat is a processor or memory parity error?Parity checking is the storage of an extra binary digit (bit) in order to represent the parity (odd or even) of a small amount of computer data (typically one byte) while memory parity error that data is stored in memory. The parity value calculated from the stored data is then compared to the final parity value. If these two values differ, this indicates a data error, and at least one bit must have been changed due to data corruption.Within a computer system, electrical or magnetic interference from internal or external causes can cause a single bit of memory to spontaneously flip to the opposite state. This event makes the original data bits invalid and is known as a parity error.Such memory errors, if undetected, may have undetectable and inconsequential results or may cause permanent corruption of stored data or a machine crash.There are many causes of memory parity errors, which are classified as either soft parity errors or hard parity errors.Soft ErrorsMost parity errors are caused by electrostatic or magnetic-related environmental conditions.The majority of single-event errors in memory chips are caused by background radiation (such as neutrons from cosmic rays), electromagnetic interference (EMI), or electrostatic discharge (ESD). These events may randomly change the electrical state of one or more memory cells or may interfere with the circuitry used to read and write memory cells.Known as soft parity errors, these events are
odd parity VRC - vertical redundancy check bit LRC - longitudinal redundancy check BitLocker Hard Drive Encryption bit flip bit rate dirty bit Parity checking uses parity bits to check that data has been transmitted accurately. The parity bit is added to every data unit (typically seven or eight bits) that are transmitted. The parity bit for each unit is set so that all bytes have either an odd number or an even number of set bits. How Parity Checking Works Assume, for example, that two devices are communicating with even parity (the most common form of parity checking). As the transmitting device sends data, it counts the number of set bits in each group of seven bits. If the number of set bits is even, it sets the parity bit to 0; if the number of set bits is odd, it sets the parity bit to 1. In this way, every byte has an even number of set bits. On the receiving side, the device checks each byte to make sure that it has an even number of set bits. If it finds an odd number of set bits, the receiver knows there was an error during transmission. The sender and receiver must both agree to use parity checking and to agree on whether parity is to be odd or even. If the two sides are not configured with the same parity sense, communication will be impossible. Parity Checking is Basic Error Detection Parity checking is the most basic form of error detection in communications. Although it detects many errors, it is not foolproof, because it cannot detect situations in which an even number of bits in the same data unit are changed due to electrical noise. There are many other more sophisticated protocols for ensuring transmission accuracy, such as MNP and CCITT V.42. Parity checking is used not only in communications but also to test memory storage devices. Many PCs, for example, perform a parity check on memory every time a byte of data is read. PREVIOUSparityNEXTpark Related Links Memory Errors, Detection and Correction TECH RESOURCES FROM OUR PARTNERS WEBOPEDIA WEEKLY Stay up to date on the l