The Diag64cart is a C64/C128 cartridge PCB, that is especially made for the need of diagnostic software, like Dead Test Rev. 781220 and Diagnostic Rev. 586220. The Diag64cart is derived from the Versa64cart (https://github.com/bwack/Versa64Cart), it lacks of the ability to be a 16k cartridge, though. The geometry of this cart was especially made for the cheap Maszczyk KM-20 and the Kradex Z7 cartridge cases. Those are available from https://restore-store.de/ or https://www.tme.eu. Dead Test and Diagnostic reside in two different address spaces of the C64. Also, they are differently configured via GAME or EXROM and use different chip select signals (ROMH or ROML).