Another nifty feature of nForce is the communication interface between its north and south bridge, the IGP and MCP. Instead of the traditional PCI-bus or the new 266 MB/s interface used by Intel (hub architecture) and VIA (V-Link), nForce is using AMD's HyperTransport interface, formerly known as LDT (lightning data transfer). This interface is also only 8-bit wide to keep motherboard makers happy, but it is clocked at 400 MHz and it is differential (kinda DDR), which gives it a bandwidth of 400 MB/s upstream and 400 MB/s downstream, adding up to 800 MB/s. It ensures high data throughput between the two chips, which is required by many streaming applications, such as audio and video recording or replay. Network throughput is also accelerated, especially in combination with the StreamThru-feature of the MCP.
APU - The Audio Processing Unit
NVIDIA admits it blatantly, the integrated sound subsystem of nForce is identical to what will make the noise in the Xbox. This however is certainly no bad news, but rather a recommendation. NVIDIA with its fetish to call its products in a way that makes them sound like 'CPU' christened this sound unit 'APU'.
This APU comes with features that blow away every sound card that's currently on the market, which is even more impressive when you consider that the APU is integrated into nForce's south bridge 'MCP' and not a discrete card. Let's have a look at its specs:
- Hardware DirectX8 audio processor (the first of its kind)
- Up to 256 different stereo voices, of which 192 are 2D-voices and 64 are 3D-voices
- Dolby Digital 5.1 Encoder
- DSL2-acceleration (Downloadable Sample Version 2)
- 32 bin mixer, with 8 voice volumes mixed to each bin (to get to 256)
NVIDIA classifies nForce's APU as a 'multi-processor audio rendering engine, as you can see in above picture. The APU renders completely to system memory, which allows the resulting stream to be sent to an AC97 codec or a USB-speaker system, in case if a nForce user fancies that. The voice processor is a fixed function DSP (digital signal processor), while the global processor is a programmable DSP. Together with the setup engine, that sets up all the data and parameters and controls all the resources required by the two DSPs, this unit is the most powerful sound subsystem found in PCs today.