Computer Memory Error Detection
Contents |
computer data storage that can detect and correct the most common kinds of internal data corruption. ECC memory is used in most computers where data corruption cannot be tolerated under any circumstances, memtest memory error detected such as for scientific or financial computing. Typically, ECC memory maintains a memory system
Uncorrectable Memory Error Previously Detected
immune to single-bit errors: the data that is read from each word is always the same as the data that had uncorrectable memory error previously detected dell been written to it, even if one or 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 memory error detected copying between 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 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
Error Detection In Computer Networks
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 of arrays of commercial DRAM chips. Thanks to built-in EDAC functionality, spacecraft's engineering telemetry reports the number of (correctable) single-bit-per-word errors and (uncorrectable) double-bit-per-word errors. During the first 2.5years of flight, the spacecraft reported a nearly constant single-bit error rate of about 280errors per day. However, on November 6, 1997, during the first month in space, the number of errors increased by more than a factor of four for that single day. This was attributed to a solar particle event that h
of pages. error detection methods in computer networks The general rule of thumb is that the information on the
Error Detection Techniques In Computer Networks
site is displayed in the "Contents" frame, called "C", while the links deeper into the structure are in the https://en.wikipedia.org/wiki/ECC_memory "Index" frame, called "I". You can find information on the site without using frames in three different ways: Some text browsers, like Lynx, don't support frames but allow browsing of framed sites by providing links to each http://www.pcguide.com/ref/ram/err.htm frame from this page. If you see links to "I" and "C" above this text, you can use these links to travel the site. You can use the search engine to perform full text searches on the site. You can use the no-frames version of the Topic Index. This will let you move quickly to most areas of the site without using frames. Sincerely, Charles M. Kozierok Webslave, The PC Guide Home - Search - Topics The PC Guide (http://www.PCGuide.com) Copyright 1997-2004 Charles M. Kozierok.All Rights Reserved. Not responsible for any loss resulting from the use of this site. Please read the Site Guide before using this material.
» Articles » Monitoring Memo... Login Error Detection and Correction Jeff Layton Data protection and checking takes place various places throughout a system. Some of it is in hardware and some of it is in software. The goal is to http://www.admin-magazine.com/Articles/Monitoring-Memory-Errors ensure that data is not corrupted (changed), either coming from or going to the hardware or in the software stack. One key technology is ECC memory (error-correcting code memory).The standard ECC memory used in systems today can detect and correct what are called single-bit errors, and although it can detect double-bit errors, it cannot correct them. A simple flip of one bit in a byte can make a drastic difference in the value of the byte. For example a memory error byte (8 bits)with a value of 156 (10011100)that is read from a file on disk suddenly acquires a value of 220 if the second bit from the left is flipped from a 0 to a 1 (11011100) for some reason.ECC memory can detect the problem and correct it so with the user unaware. Notice, however, that only one bit in the byte has been changed and then corrected. If two bits change – perhaps by both the second in computer networks and seventh from the left – the byte is now 11011110 (i.e., 222); typical ECC memory can detect that the “double-bit” error occurred, but it cannot correct it. In fact, when a double-bit error happens, memory should cause what is called a “machine check exception” (mce), which should cause the system to crash. After all, you are using ECC memory, so ensuring the data is correct is important; if an uncorrectable memory error occurs, you would probably want the system to stop.The source of bit-flipping usually originates in some sort of electrical or magnetic interference inside the system. This interference can cause a bit to flip at seemingly random times, depending on the circumstances. According to the Wikipedia article and a paper on single-event upsets in RAM, most single-bit flips are the result of background radiation – primarily neutrons from cosmic rays.The same Wikipedia article reports that the error rates reported from 2007 to 2009 varied all over the map, ranging from 10–10 (errors/bit-hr) to 10–17 (seven orders of magnitude difference). The lower number is just about one error per gigabit of memory per hour. The upper number indicates roughly one error every 1,000 years per gigabit of memory.A study of real memory errors took place at Google. During their investigations they found that one third of the machines and more than 8 percent of the DIMMs saw correctable errors per year. This