Memory tester: Difference between revisions

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{{Short description|Computer memory testing equipment}}

{{refimprove|date=May 2020}}

{{use dmy dates|date=December 2021|cs1-dates=y}}

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* Incorrect IC mask, (Manufacturing problem)

* Functional design errors (logical function that had to be implemented, is designed incorrectly).

* Defective storage cell

=== Non-permanent faults ===

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{{Reflist|refs=

<ref name="AMT">{{cite web |title=Innoventions Ramcheck Advanced Memory Tester - PCSTATS.com |website=www.pcstats.com |url=http://www.pcstats.com/articleview.cfm?articleID=1174}}</ref>

<ref name="Vector">{{cite book |title=The Worm Memory Test |publisher=[[Vector Graphic]] |date=2015-10-21<!-- upload date --> |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.)</ref>

<ref name="Wilkinson_2003">{{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]] uses half of the cycle to [[RAM refresh|refresh]] the [[dynamic RAM]]. […] since the Z80 must spend half of each [[instruction fetch]] 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]]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]], not from RAM […] result[ing] in the [[Heath H89|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 [[cathode-ray tube|CRT]] 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 [[self-relocation (computing)|relocation]]. Incidentally, the program is called a [[computer worm|worm]] test because, as the RST 7 instruction moves up through memory, it leaves behind a [[NOP trail|slime trail]] of [[NOP (code)|NOP]]s (NO OPERATION). […]}}</ref>

<ref name="Wilkinson_2003">{{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 }}</ref>

<ref name="Steinman_1986_Worm">{{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=<!-- |number=-->#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 }} [https://ia803109.us.archive.org/13/items/dr_dobbs_journal_vol_11/dr_dobbs_journal_vol_11.pdf] (2 pages)</ref>

<ref name="Steinman_1986_Toolbox">{{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]] / [[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)</ref>

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