I've got several bad 4164s -- Microns pulled from an Apple 2 repair. Are you still unable to make it to TASM? I can post a couple to you if so.
-Josh On Fri, Sep 13, 2019 at 7:54 PM Jeffrey Birt <[email protected]> wrote: > > I built a DRAM tester for fun and to brush up on Arduino development. I have > a lot of students I work with use Arduino, so I wanted to build something to > stay up to date and I have not done anything with an Arduino for more than a > year. I found a project online as a starting point and added an automatic > DRAM refresh driven by Timer2 overflow. Even with a pokey Arduino and the ISR > in C it can refresh 64 rows in less and 100us. > > I did a quick test with a 41256 just now and was happy I could read/write all > bits successfully. Then I realized I don’t have any known bad 4164/41256 type > DRAM chips on hand. So, if you happen to have a few bad DRAM chips on hand > and you’re in the USA I would gladly take them off your hands. Otherwise I’ll > have to figure out a way to inject a simulated fault. Maybe writing a wrong > value to a known cell after writing the proper pattern to all cells would be > a good enough simulation? > > I still have a way to go with the software. The original project I found > online used separate functions for each test pattern. I want to create a > single function that will write a bit pattern that is passed to it and then > verify that pattern is in memory. Maybe a n second pause would be good to > have in place between the write and verify to ensure that the refresh is > working properly? > > Thanks, > Jeff Birt > >
