Hardware mixing
Hardware mixing is a performance feature of computer audio hardware which enables sound cards to receive multiple audio streams and play them all at the same time. Hardware mixing improves performance by offloading audio mixing operations from the CPU and performing them on dedicated hardware. In addition to mixing, the hardware performs related operations such as sample rate conversion (SRC), attenuation, and, optionally, 3D processing that would otherwise need to be performed in software. On Microsoft Windows, hardware mixing is also referred to as hardware buffering or as DirectSound hardware acceleration.
Those cards which offer hardware mixing include professional multichannel audio interfaces, currently manufacturers do not indicate if a sound card uses a hardware mixing capability. Some manufacturers list features provided by the driver(software) which would indicate the sound device being a software driven card and not incorporating a hardware mixer. In the Windows Operating System, DxDiag can be used to test if the audio hardware supports hardware mixing.