This is a Arduino sketch to test Hitachi HM4864P-2 dynamic memory chips, used in some Commodore C64 boards. It was written using plain avr-libc omitting the Arduino bootloader, mainly due to poor switching speed of Arduino's digitalWrite() (overhead up to 40 times slower) and 10us upper limit for HM4864P-2 RAS strobe.

All you need are:

• Arduino Uno or any pin compatible board.
• ISP programmer (I use stk500 compatible programmer).
• A single HM4864P-2 chip.
• Optionally, a single LED if the built-in LED on pin 13 (PB5) is not visible enough.
• avr-gcc
• avr-libc
• AVRDUDE

Upon successful build of the circuit as shown below, attach (via the ICSP connector) and set the proper ISP programmer device in Makefile, and then just type in:

make flash

This will build the firmware and flash it to the connected device.

• LED is glowing continuously - memory chip has passed all tests.
• LED is blinking - memory chip is damaged.

• This is a simple educational project, and was developed to this sole purpose.
• Nevertheless, you should be able to diagnose failed memory chips in your Commodore C64 board.
• I take no responsibility for any negative outcomes or damage you may cause using this project.