DRAM and SRAM testing

General discussion for retro computing
alvin
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DRAM and SRAM testing

Post by alvin »


The author of the interface arrived on the forum and suggested a few more interesting arguments for using dedicated testers. I must say that I fully agree with it :) Let me quote it in the original :)
trojacek is right, it is not possible to check for correct timings, even very expensive testers with much more power as a ATmega2560 cannot do this perfectly.
There are several issues a "simple" tester cannot do:
- checking timings: you need a very high resolution of 1-5ns to check if a rising or falling flank is correct. Only very expensice equipment (e.g. from Fluke) can reach this resolution.
- correct level of signals: you have to use analog ports to check if a signal level is correct. You have to measure the signal levels during the testing and check if the TTL levels are correct.
What a simple tester can do:
- it can check of a memory cell is in principle working
- it can check if refreshing is working in principle
- it can check if a row or column line is not working correctly
These simple tests can detect 99.9% of defect memory chips for an affordable price. Maybe you will have a false positive (you will recognize when you use this chip) or a false negative (then you loose one chip) but you will still have false positives and negatives also with expensive testig equipment.
So affordable memory testers are a good compromise (or spending thousands of EUR for having maybe 0.5% more accurate tests?).
Testing in a real computer is never a good idea. Depending on the number of RAM chip you want to test, you have to switch the computer on and off several times that will stress the old hardware and maybe this will lead to other defects. Also mounting and dismounting chips several times will stress the old sockets. So not really a good idea.
I have tested hundreds of chips whith it now and will not longer miss it. Also the feature to identify (EP) ROMs is great. I have quite often ROMs that are not labeled, and it is really convenient to put these in the tester and see that is e.g. a "901447-05 / 39-03 (H3) / PET Basic 1/2 $ E0" ROM;)
And you can use the tester to create your own tests. The hardware ports are documented, so you can write also your own software if you want.
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SanderoCaro
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DRAM and SRAM testing

Post by SanderoCaro »


As I can see, apart from DRAM (and ROM, EPROM, SRAM), you can test a lot of digital circuits. But I can't read if there is a need to set the chip type somewhere, or if there is any autodetection.
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NamelessOne
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DRAM and SRAM testing

Post by NamelessOne »


from what I can see in the documentation (and on YouTube videos), the procedure is as follows:
1) You choose the type of chip to be tested
2) the display shows the position in which to set the switches on the card (power supply to the system)
3) you are doing the test
I have no name and never will have.
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PanzerGeneral
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DRAM and SRAM testing

Post by PanzerGeneral »


with a human interface
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Wariorr
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DRAM and SRAM testing

Post by Wariorr »


Interesting design, but the guy only sells a cash for around $ 120.
Although you can buy it through Paypal, I do not know if I would spend that much on it, when I have similar functions in the universal programmer, maybe except for Russian systems, but I can add test signatures myself (the only drawback is the lack of Cyrillic in the descriptions of elements)
I'm a great warrior of old lore.
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KillJoy
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DRAM and SRAM testing

Post by KillJoy »


Count how much the ready made by PABB will cost. Here you have a combine, which you can even operate from the computer and in the housing.
i'm gonna kill all you joy.
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Openmind
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DRAM and SRAM testing

Post by Openmind »


I once again asked Stephan, the one who sells the CDs "at cost". He wanted to sell me two sets of bare plates only, with shipping for 66 Euro. I wrote back to him that in the description the phrase "at the cost" is a big mistake. When you buy the plates only, you don't know if it will work, and then if it doesn't work, you don't know if it is due to a design defect or a folding error. It's soviet at least you get running. The guest designed it, programmed it, launched it, tested it and has at least a ready, working product that he can evaluate as he wants.
nothing goes here for now
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Iknownothingatall
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DRAM and SRAM testing

Post by Iknownothingatall »


Everything is great, but it is not known how reliable the test results are in the case of DRAM memory, because it is quite difficult to do well.
Someone has to risk it and spend money first to find out. ;)
At this price of the device, I prefer to stay with my used programmer, which also has the DRAM / SRAM / TTL / CMOS testing functions and on which I spent half of this amount ... :)
Probably the DRAM tests will not be more reliable as I think, and can only provide an initial selection for the price of $ 120.
i know that i know nothing at all.
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MovieDirector@
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DRAM and SRAM testing

Post by MovieDirector@ »


I have half a bucket of SIMM-30 memory to test and then the testing device would go to the shelf ... But wait - it is not possible to test SIMMs. Most TTL systems can be tested much cheaper TL866 which boils down to the fact that 120 bucks could buy me an interesting solution to the problem that I do not have ...
I'm gonna direct a movie someday...
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SummerFLower
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DRAM and SRAM testing

Post by SummerFLower »


You can make a special adapter for "small" SIMMs, where you will switch data lines with jumpers because SIMMs usually have a bit more than the chip itself
i just strartedt to bloon this summer.
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