Re: In search of bad 4164, 41256 DRAM

From: Gerrit Heitsch <gerrit_at_laosinh.s.bawue.de>
Date: Mon, 14 Oct 2019 16:19:23 +0200
Message-ID: <45d218fe-c8e9-6067-6fb5-15380b4d290e_at_laosinh.s.bawue.de>
On 10/13/19 9:40 PM, Jeffrey Birt wrote:
> Thanks Dave, I’ve read about the MARCH tests previously and to my 
> understanding parts of these tests are designed to find addressing 
> errors and/or for multi-bit wide memories. There is also the issue on 
> modern processors with making sure that you just not writing/reading 
> to/from cache.
> 
> I did just finish up adding a ‘walking value’ test which fill the memory 
> with all zeros or ones and steps through each bit, confirms it is still 
> at the fill state, changes the state and tests for the changed state. 
> This should hopefully help catch any internal addressing (row/column) 
> errors where a write might write to adjacent cells as well.

That wouldn't catch an error where 2 adjacent cells (physically, not 
necessarily adresswise) developed a short circuit. To catch this error, 
you'd have to fill the RAM, verify that state, then flip the bit in 
question and verify it is indeed flipped. So far so good... but now you 
have to check the RAM for additional flipped bits.

  Gerrit
Received on 2020-05-29 23:06:48

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