indicate a severe hardware or software problem that prevented startup from occurring successfully. The Sad Mac icon is displayed, along with a set of hexadecimal codes that indicate the type of problem at startup. Different codes are for different errors. This is in place of the normal Happy Mac icon, which indicates that the startup-time hardware tests were successful. In 68k models made after the Macintosh II, the Chimes of Death are played. Models prior to the Macintosh II crash silently and display the Sad Mac, without playing any tone. PowerPC Macs play a sound effect of a car crash, and computers equipped with the PowerPC upgrade card use the three note brass fanfare death chime (A, E-natural, and E-flat), followed by the sound of a drum, same as the Macintosh Performa 6200 and Macintosh Performa 6300. A Sad Mac may be deliberately generated at startup by pressing the interrupt switch on Macintosh computers that had one installed, or by pressing Command and Power keys shortly after the startup chime. On some Macintoshes such as PowerBook 540c, if the user presses the command and power keys before the boot screen displays, it will play the "chimes of death". The chimes are a fraction of normal speed and there is no Sad Mac displayed. Old World ROM Power Macintosh and PowerBook models based on the PCI architecture do not use a Sad Mac icon and will instead only play the error/car-crash sound on a hardware failure (such as missing or bad memory, unusable CPU, or similar). Mac OS X 10.2 Jaguar and later instead use the Universal "no" symbol to denote a hardware or software error that renders the computer non-bootable. Chimes of Death The Chimes of Death are the Macintosh equivalent of a beep code on IBM PC compatibles. On all Macintosh models predating the adoption of PCI and Open Firmware, the Chimes of Death are often accompanied by a Sad Mac icon in the middle of the screen. Different Macintosh series have different death chimes. The Macintosh II is the first to use the death chimes, a loud and eerie upward major arpeggio, with different chimes on many models. The Macintosh Quadra, Centris, Performa (including the 6200 and 6300, which were also Power Macintosh models, only occurring after the screen lights up), LC, and the Macintosh Classic II play a generally softer and lower pitched version of the upward