Memory testers are specialized test equipment used to test and verify memory modules.

Types

Memory module testers can be broadly categorized into two types, hardware memory testers and

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

diagnostic program A diagnostic program (also known as a Test Mode) is an automatic computer program sequence that determines the operational status within the software, hardware, or any combination thereof in a component, a system, or a network of systems. Diagno ...

s that run in a PC environment. Hardware memory testers have more sophisticated and comprehensive test features built into the tester as compared to software diagnostic testing programs. Software diagnostic does allow for detection of possible problems when memory modules are already installed on the computer system.

Hardware testers

High-end

automatic test equipment Automatic test equipment or automated test equipment (ATE) is any apparatus that performs tests on a device, known as the device under test (DUT), equipment under test (EUT) or unit under test (UUT), using automation to quickly perform measurements ...

(ATE) Class Memory testers are used by most OEM memory chip manufacturers such as Samsung, Hyundai, Micron…etc. They are typically priced starting at one million dollars per system. This equipment must be operated by well trained semiconductor engineers. ATE Class Memory testers are built with very complex test algorithms to detect memory faults during the final stages of memory chip packaging. Mid-range memory testers typically priced under $26,000, and are commonly found in memory module manufacturing assembly houses. These testers are built to support mass volumes of memory module testing. They are also used for detecting assembly faults caused by mis-soldering and cross-cell contamination after chips are assembled onto

PCB PCB may refer to: Science and technology * Polychlorinated biphenyl, an organic chlorine compound, now recognized as an environmental toxin and classified as a persistent organic pollutant * Printed circuit board, a board used in electronics * ...

or SIMM cards. These memory testers are usually docked onto an automatic handling system for high volume production testing, thus eliminating manual intervention by an operator. Low-end memory testers are usually relatively low cost ranging from $1000 – $3000. Their main features are portability, ease of use and relatively small size. They are typically used by the service industry especially by computer service technicians, RMA departments, memory reseller/brokers/ and wholesalers for verifying and testing memory modules that fails in PC system or before going into PC. Quality and features of this range of memory testers varies greatly depending on the manufacturer. A good memory tester is built with features comparable with high-end ATE and medium range memory tester. The key is to provide a simple to use tester at an affordable price that is still effective in capturing most memory faults and failures.

Software testers

Memory diagnostic software programs (e.g.,

memtest86 MemTest86 and Memtest86+ are memory test software programs designed to test and stress test an x86 architecture computer's random-access memory (RAM) for errors, by writing test patterns to most memory addresses, reading back the data, and com ...

) are low-cost or free tools used to check for memory failures on a PC. They are usually in the form of a bootable software distribution on a

floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined w ...

CD-ROM A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both comput ...

. The diagnostic tools provide memory test patterns which are able to test all system memory in a computer. Diagnostic software cannot be used when a PC is unable to

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due to memory or

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. While in principle a test program could report its results by sending them to a storage device (e.g., floppy disc) or printer if working, or by sound signals, in practice a working display is required.

Worm memory tests

Some stronger memory tests capable of detecting subtle timing problems are implemented as self-modifying, dynamically self-relocating and potentially self-destructive memory

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s called ''worm memory test'' (or ''worm test'').

Detected faults

Memory testers are designed to detect two types of faults that affect the functional behavior of a system (memory chip, logic chips or PCB board): Non-Permanent faults and Permanent faults.

Permanent faults

Permanent faults affect the logic values in the system permanently, these faults are easier to detect using a memory tester. Examples include: * Incorrect connections between

integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...

s, boards, etc. (e.g. missing connections or shorts due to solder splashes or design fault) * Broken component or parts of components * Incorrect IC mask, (Manufacturing problem) * Functional design errors (logical function that had to be implemented, is designed incorrectly).

Non-permanent faults

Non-Permanent faults occur at random moments. They affect a system's behavior for an unspecified period of time. The detection and localization of non-permanent faults are extremely difficult with a memory tester. Sometimes non-permanent faults will not affect the system's operation during testing. There are two types of non-permanent faults: Transient fault and Intermittent fault. Transient faults are hard to detect, and there are no well defined faults to detect. Errors in RAM introduced by transient faults are often called software errors, the following examples are possible factors that will contribute to transient faults: *

Cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...

(

UV light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...

) *

Alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produce ...

(Dust) *

Pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

Humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depe ...

Temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

Pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

Vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic function, periodic, such as the motion of a pendulum ...

Power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a r ...

fluctuations *

Electromagnetic interference Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electros ...

* Static electrical discharges * Ground loops Intermittent faults are caused by non-environmental conditions such as: * Loose connections * Deteriorating or aging components * Critical timing *

Resistance Resistance may refer to: Arts, entertainment, and media Comics * Either of two similarly named but otherwise unrelated comic book series, both published by Wildstorm: ** ''Resistance'' (comics), based on the video game of the same title ** ''T ...

and

capacitance Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...

variation * Physical irregularities * Noise (noise disturbs signals in the system)

References

{{Reflist, refs= {{cite web , title=Innoventions Ramcheck Advanced Memory Tester - PCSTATS.com , website=www.pcstats.com , url=http://www.pcstats.com/articleview.cfm?articleID=1174 {{cite book , title=The Worm Memory Test , publisher=

Vector Graphic Vector graphics is a form of computer graphics in which visual images are created directly from geometric shapes defined on a Cartesian plane, such as points, lines, curves and polygons. The associated mechanisms may include vector display a ...

, date=2015-10-21 , orig-date= , url=http://deramp.com/downloads/vector_graphic/software/manuals/Worm.pdf , access-date=2021-12-13 , url-status=live , archive-url=https://web.archive.org/web/20190515181617/http://deramp.com/downloads/vector_graphic/software/manuals/Worm.pdf , archive-date=2019-05-15 (3 pages) (NB. From a Vector Graphic 3 service manual.) {{cite web , title=The H89 Worm: Memory Testing the H89 , author-first=William "Bill" Albert , author-last=Wilkinson , date=2003 , orig-date=1996, 1984 , work=Bill Wilkinson's Heath Company Page , url=https://www.heco.wxwilki.com/h89worm.html , access-date=2021-12-13 , url-status=live , archive-url=https://web.archive.org/web/20211213130013/https://www.heco.wxwilki.com/h89worm.html , archive-date=2021-12-13 , quote= ��Besides fetching an instruction, the

Z80 The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples were ...

uses half of the cycle to refresh the

dynamic RAM Dynamic random-access memory (dynamic RAM or DRAM) is a type of random-access semiconductor memory that stores each bit of data in a memory cell, usually consisting of a tiny capacitor and a transistor, both typically based on metal-oxide ...

. ��since the Z80 must spend half of each

instruction fetch The instruction cycle (also known as the fetch–decode–execute cycle, or simply the fetch-execute cycle) is the cycle that the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instruction ...

cycle performing other chores, it doesn't have as much time to fetch an instruction byte as it does a data byte. If one of the

RAM chip Random-access memory (RAM; ) is a form of computer memory that can be read and changed in any order, typically used to store working data and machine code. A random-access memory device allows data items to be read or written in almost the s ...

s at the memory location being accessed is a little slow, the Z80 may get the wrong bit pattern when it fetches an instruction, but get the right one when it reads data. ��the built-in memory test won't catch this type of problem ��it's strictly a data read/write test. During the test, all instruction fetches are from the

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * R ...

, not from RAM ��result ngin the H89 passing the memory test but still operating erratically on some programs. ��This is a program that tests memory by relocating itself through RAM. As it does so, the CPU prints the current address of the program on the

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and then fetches the instruction at that address. If the RAM ICs are okay at that address, the CPU relocates the test program to the next memory location, prints the new address, and repeats the procedure. But, if one of the RAM ICs is slow enough to return an incorrect bit pattern, the CPU will misinterpret the instruction and behave unpredictably. However, it's likely that the display will lock up showing the address of faulty IC. This narrows the problem down eight ICs, which is an improvement over having to check as much as 32. ��The ��program will perform a worm test by pushing an RST 7 (RESTART 7) instruction from the low end of memory on up to the last working address. The rest of the program remains stationary and handles the display of the current location of the RST 7 command and its relocation. Incidentally, the program is called a

test because, as the RST 7 instruction moves up through memory, it leaves behind a

slime trail Snail slime (''mucopolysaccharide'') is a kind of mucus (an external bodily secretion) produced by snails, which are gastropod mollusks. Land snails and slugs both produce mucus, as does every other kind of gastropod, from marine, freshwater, ...

of NOPs (NO OPERATION). ��} {{cite journal , title=The Worm Memory Test , author-first=Jan W. , author-last=Steinman , location=West Linn, Oregon, USA , journal= Dr. Dobb's Journal of Software Tools for the Professional Programmer , publisher= M&T Publishing, Inc. / The People's Computer Company , publication-place=Redwood City, California, USA , department=The Right to Assemble (TRTA) , volume=11 , issue=9 , id=#119. ark:/13960/t74v34p9p {{CODEN, DDJOEB , issn=1044-789X , date=1986-09-01 , pages=114–115 (662–663) , url=https://archive.org/details/dr_dobbs_journal_vol_11/page/662/mode/1up , access-date=2021-12-13 , url-status=live}

(2 pages) {{cite book , title=Dr. Dobb's Toolbook of 68000 Programming , chapter=III. Useful 68000 Routines and Techniques, 16. The Worm Memory Test , author-first=Jan W. , author-last=Steinman , location=West Linn, Oregon, USA , publisher= Brady Book /

Prentice Hall Press Prentice Hall was an American major educational publisher owned by Savvas Learning Company. Prentice Hall publishes print and digital content for the 6–12 and higher-education market, and distributes its technical titles through the Safari B ...

/ Simon & Schuster, Inc. , publication-place=New York, USA , date=1986 , pages=341–350 , lccn=86-25308 , isbn=0-13-216649-6 , chapter-url=http://www.bytesmiths.com/Publications/Worm%20Memory%20Test%20-%20Steinman_1986-01-01-1.pdf , access-date=2021-12-13 , url-status=live , archive-url=https://web.archive.org/web/20211213202006/http://www.bytesmiths.com/Publications/Worm%20Memory%20Test%20-%20Steinman_1986-01-01-1.pdf , archive-date=2021-12-13 (1+5+10+1 pages) Computer memory Utility software types