interchangeably to indicate the degree of polyphony, not the output speaker configuration. For example, much older sound chips could accommodate three voices, but only one output audio channel (i.e., a single mono output), requiring all voices to be mixed together. Later cards, such as the AdLib sound card, had a 9-voice polyphony combined in 1 mono output channel. Early PC sound cards had multiple FM synthesis voices (typically 9 or 16) which were used for MIDI music. The full capabilities of advanced cards are often not fully used; only one (mono) or two (stereo) voice(s) and channel(s) are usually dedicated to playback of digital sound samples, and playing back more than one digital sound sample usually requires a software downmix at a fixed sampling rate. Modern low-cost integrated sound cards (i.e., those built into motherboards) such as audio codecs like those meeting the AC'97 standard and even some lower-cost expansion sound cards still work this way. These devices may provide more than two sound output channels (typically 5.1 or 7.1 surround sound), but they usually have no actual hardware polyphony for either sound effects or MIDI reproduction these tasks are performed entirely in software. This is similar to the way inexpensive softmodems perform modem tasks in software rather than in hardware. In the early days of wavetable synthesis, some sound card manufacturers advertised polyphony solely on the MIDI capabilities alone. In this case, typically, the card is only capable of two channels of digital sound and the polyphony specification solely applies to the number of MIDI instruments the sound card is capable of producing at once. Modern sound cards may provide more flexible audio accelerator capabilities which can be used in support of higher levels of polyphony or other purposes such as hardware acceleration of 3D sound, positional audio and real-time DSP effects. List of sound card standards Color codes Connectors on the sound cards are color-coded as per the PC System Design Guide. They may also have symbols of arrows, holes and soundwaves that are associated with each jack position. History of sound cards for the IBM PC architecture Sound cards for IBM PC compatible computers were very uncommon until 1988. For the majority IBM PC users, the internal PC speaker was the only way for early PC software to produce sound and music. The speaker hardware was typically limited to square waves. The resulting sound was generally described