DRAMscope Can Diagnose a Commodore 64 Even When Its RAM Is Too Dead to Help

Developer bitbarista releases DRAMscope v1.6, an open-source EasyFlash diagnostic cartridge that boots in Ultimax mode without working C64 RAM.

A new open-source diagnostic cartridge called DRAMscope tackles one of vintage-computing repair's more irritating paradoxes: how do you run a memory test when the computer's memory is precisely the bit that has stopped cooperating? Developer bitbarista created DRAMscope while working on DRAMa Free 64, an FPGA-based replacement for the C64's eight original 4164 DRAM chips, and has now turned the diagnostic code into a standalone EasyFlash cartridge. DRAMscope boots in Ultimax mode from its own reset vector, meaning it does not require working system RAM or even a functional KERNAL ROM to start. The developer has verified this behaviour on real hardware with every main DRAM chip physically removed.

Once running, it performs walking-bit, address-line, March B, March LR, row-and-column and retention tests, separately checks colour RAM and maps failing locations. On eight-chip C64 boards it can even identify the likely 4164 associated with a failed data bit. Version 1.6 fixes a false PLA diagnosis and improves interrupt handling.

There are sensible caveats: genuinely faulty DRAM chips and two-chip 41464 boards still need more real-world validation. Even so, a free MIT-licensed diagnostic capable of waking up inside a C64 whose RAM has effectively left the building is exactly the sort of tool keeping forty-year-old hardware alive.