Re: In search of bad 4164, 41256 DRAM

Checkout the MARCH-B and MARCH-C tests. These are specifically designed to
pickup lots of odd errors like this. There are some excellent papers on
interaction between memory cells in DRAM.

Dave


On Sun, 13 Oct 2019 at 14:37, Jeffrey Birt <birt_j_at_soigeneris.com> wrote:

>
> >>Yes, if 2 cells next to each other get shorted together for whatever
> reason >>you will not find them if you fill the whole DRAM with zeros or
> ones.
>
> >>But even 0x55 and 0xAA won't find all possible faults. Grab memtest86+
> >>and take a look at all the patters it uses (it tells you while it's
> running).
>
> I have looked at a few test programs like this and they are written with
> multi-bit wide memory in mind. When testing a single bit wide DRAM most of
> these tests will not yield any benefit (I think) as the tests are designed
> to alternately set adjacent bits by using a variety of strategies which one
> can do directly when testing a single DRAM chip.
>
> One thing that caught my eye in the explanations of test for memtest86+
> was the walking ones test which might be useful so I'll ad that test in and
> see what happens.
>
> Jeff Birt
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