RE: In search of bad 4164, 41256 DRAM

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.

 

Now to clean up the code and update the schematic…

 

Jeff Birt

 

From: David Roberts <daver21145_at_gmail.com> 
Sent: Sunday, October 13, 2019 10:32 AM
To: cbm-hackers_at_musoftware.de
Subject: Fwd: In search of bad 4164, 41256 DRAM

 

The MARCH-B and MARCH-C algorithms are described in http://ww1.microchip.com/downloads/en/Appnotes/00001778A.pdf with the actual fault scenarios being described in https://www.edn.com/design/integrated-circuit-design/4439803/Memory-fault-models-and-testing.

 

Dave