C64 Dead Test
The 586220 based diagnostic cart was used by Commodore technicians in house to diagnose problems with C64s.
When paired with a full test harness, the software exercises the CPU, system RAM, ROMs, dedicated ICs (SID, PLA, VIC, CIA, etc) and various I/O circuits of the C64. The test will report if something is bad and possibly display what IC has failed.
Refer to the manual below on proper operation and how to diagnose issues when using the 586220 cartridge.