As this is done at very low level, it is hard to make a routine that can write to the screen at any possible graphics mode, and without the OS knowing (i.e. the

As this is done at very low level, it is hard to make a routine that can write to the screen at any possible graphics mode, and without the OS knowing (i.e. the message could disappear as soon as it appears because it would have been overwritten). Given that there are no specific LEDs to indicate those kind of faults, they probably came out with this creative way of using the PC speaker (something rarely used by the OS/applications, reducing a lot the risk of interference). For clarification, this is the internal PC speaker controlled by one of the motherboard chipset timers. It can only play square waves. To play an audio message, custom additional hardware would be needed on the motherboard...