Data 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
Parity Error 5x5
bit was originally stored in additional individual memory chips; with the introduction memory parity error of plug-in DIMM, SIMM, etc. modules, they became available in non-parity and parity (with an extra bit per byte,
Parity Error System Halted
storing 9 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 also 5 References History[edit] Early parity error cisco 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 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 parity error detection 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 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
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Nmi Parity Error
View with Adobe Reader on a variety of devices Updated:Jul 15, pci parity error 2013 Document ID:116135 Document ID: 116135 Updated: Jul 15, 2013 Contributed by Shawn Wargo, Cisco Engineering. Download
Parity Error 4x4
PDF Print Feedback Related ProductsCisco Catalyst 6500 Series Switches ContentsIntroductionBackgroundSoft ErrorsHard ErrorsCommon Error MessagesProcessorRAMASICLatest AdvancementsProcessorRAMASICSoftwareMSFC IBC Reset6700 Series 'Single-Bit Parity Error' ResetRecommendationsSoft Errors (SEU)Environmental AuditLatest Firmware https://en.wikipedia.org/wiki/RAM_parity (Rommon)Thumb ScrewsHard Errors (Malfunction)Hardware (MTBF and EOL) AuditHardware DiagnosticsRelated Cisco Support Community DiscussionsIntroductionThis document describes soft and hard parity 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 http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/116135-trouble-6500-parity-00.html 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 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
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and Parallel Communication Error Detection Even Parity Error Detection Odd Parity Error Detection Error Detection: Block Check Sum Data Communications Equipment (DCE) Data Terminal Equipment (DTE) Transmission Modes Baud and Data Rates The OSI Reference Model Analogue and Digital Signals Asynchronous and Synchronous Transmission Transmission Problems Even Parity Error Detection ASCII characters are comprised of 7 bits, eg: 1000001 is a capital 'A'. However, each ASCII character is typically stored as a byte, ie: 8 bits. The 8th position is therefore unused. However, this 8th bit can be used to store a parity bit. In the even parity system the parity bit is used to ensure that the total number of 1's when added together equals an even number. Even parity works by counting the number of 1's and if the total is even then the parity bit is set to zero and if it is odd the parity bit is set to one. Thus, the total number of 1's in the byte is always even. The sender sets the parity bit before transmission and the receiver checks it on receipt and strips it if necessary. If the parity bit is found to be wrong, the character has been corrupted during transmission. No Error Detected Error Detected 01000001 01000011 11000011 11000010 Next: Odd Parity Error Detection (c) 2007 Scottish Qualifications Authority