Thanks for your 4164 DRAM tester. I built 41128 tester from your code and schematic. https://github.com/park27001/41128-DRAM-playground
I tested my probably faulty 4164 DRAM chips using the dramarduino.ino sketch (DRAMADUINO😉). It did not indicate any IC's as being faulty. The computer did still not agree and I replaced all the memory; problem solved. Then I tested the IC's using your sketch. It succesfully identifies the faulty IC (one of a batch of eight) every time.😀 Thanks for sharing the sketch! Hessel.