A Sad Mac is an iconic symbol used by older-generation Macintosh computers (hardware using the Old World ROM) to indicate a severe hardware or software problem that prevented startup from occurring successfully. The Sad Mac icon was displayed, along with a set of hexadecimal codes that indicated the type of problem at startup. This was used in place of the normal Happy Mac icon, which indicated that the startup-time hardware tests were successful. In earlier models, a tune (Chimes of Death) was played, and later models featured a digitized sound of a car crash. In the MC68000-based machines (those models earlier than the Macintosh II as well as the original Macintosh Classic), no sound was played.