Audio Processing Unit (APU)

The MCP-T also house the nForce2’s Audio Processing Unit, or APU. The APU on nForce2 has the same functionality as the original nForce with up to 6 channel audio with Dolby Digital Encoding capabilities.


The MCP-T is Dolby capable however there is a licence fee to expose the functionality hence not all motherboard makers do in all configurations, which restricts the audio capabilities of the nForce chipset. With nForce2 NVIDIA are trying to clarify which motherboard configurations will fully expose all the APU capabilities by utilising the brand ‘SoundStorm’. The following table highlights the audio capabilities of the APU and what differentiates the normal APU specifications from those that can be designated ‘SoundStorm’

 Feature

NVIDIA nForce APU

NVIDIA SoundStorm

 DSP or HW-accelerated 2D (Stereo) Voices

256 voices

256 voices

 DSP or HW-accelerated 3D Voices

64 3D voices

64 3D voices

 DX8 HW-Submixer

32 HW submixers

32 HW submixers

 DLS2 Acceleration

Yes

Yes

 Per Voice Parametric EQ

Yes

Yes

 Occlusion and Obstruction

Yes

Yes

 Near Field Effects

Yes

Yes

 EAX2 and I3DL2 Reverb

Yes

Yes

 Global Effects (Reverb, Chorus etc)

Yes

Yes

 Speakers

2 speakers

2, 4, or 6 speakers

 Microphone/Line Inputs

>Yes

Yes

 SPDIF Interface

No

Yes

 Software and Utilities

Basic

Enhanced

 H/W Dolby Digital Encode

No

Yes


SoundStorm Connection Riser Board

Interestingly NVIDIA dropped the hint that nForce2 would be the first product that the SoundStorm brand will be utilised on, however they have demonstrated others behind closed doors. What these other products are will remain a mystery at the moment however it is unlikely to be add-in sound boards as NVIDIA believe that this should be integrated.

The use of the SPDIF interconnect in conjunction with a Dolby Digital Processor allows for the APU to produce a Dolby Digital Encoded sound stream.


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Dolby Digital Setup


The nForce APU is a DirectX8 audio processor and allows for the following features to be processed in hardware, rather then the Host CPU:

  • Downloadable Sounds Version 2 (DLS2): The APU can perform layering and filtering using stereo waves as the source.
  • Effects processing on DirectSound buffers: More sophisticated sound effects as well as higher quality music and sound effects with greater production values and real-time interactive control.
  • Interactive 3D Audio Level 2 (I3DL2): Reverberation and occlusion/obstruction support.
  • Sub-mixed audio streams: Complex, rich sounds can be created by sub-mixing two or more audio streams.

In addition to the DX8 features listed above the APU can also perform the following processes in hardware:

  • Head Reference Transfer Functions (HRTF) algorithms with cross talk cancellation
  • Near field effects
  • Macro effects
  • 7-band graphic equalizer