The BLU-800 and BLU-160 are identical when it comes to DSP horsepower, the only difference being that the BLU-800 has CobraNet.
Creating a default configuration for both devices shows that the BLU-800 uses 15%, and the BLU-160 only uses 3% of DSP resource.
This is because the CobraNet module in the BLU-800 is using DSP resources, effectively leaving less user programmable DSP than the BLU-160. To understand why this is, we need to look at how the DSPs are utilized.
In the BLU-800 and BLU-160 there are two DSPs. Each DSP has 128 channels in and out of the DSP. The channels are known as Bus Ports.
The Bus Ports are a finite resource and are part of what makes up the DSP resource usage meter. If you double click the DSP resource meter in Audio Architect, you can see the individual resource values for each DSP in the Advanced Resource Usage Dialog. The channels in and out of the DSPs are referred to as BusRx and BusTx Ports.
The ‘Worst Case Usage’, which is what is displayed on the meter, uses the highest individual resource value. In the dialog above, it would be the BusRx Ports (the average of DSP0 and DSP1).
Sometimes, either because a single processing object can’t fit on to a single DSP or the signal path extends across both DSPs, the compiler must use some of those Bus Ports to pass the audio between DSPs. If this happens, you may notice a big jump in resource usage, as a lot more Bus Ports are used.
In configurations with large matrices (matrix mixer and matrix router), it is nearly always the Bus Ports which are exhausted first. If we have a BLU-160 with no cards installed (0x0), it is possible to have a 128x128 matrix router, with 128 BLU link channels in and 128 BLU link channels out. The matrix needs to be split across the two DSPs since a single DSP is not powerful enough. Each DSP is handling 128 inputs and 64 outputs, hence each DSP is using 128 BusRx Ports, and 64 BusTx Ports. Because all the BusRx Ports to both DSPs are being used, the resource meter will show 100%. The DSP cycles however will be below 100%. It is therefore possible to still add some DSP processing without going over 100%, so long as no additional processing objects need to span over two DSPs, and an audio path does not go over two DSPs.
It is important to note, that the 128x128 matrix with BLU link as described above will not work in a BLU-800. This is because the BLU-800 has CobraNet, this is also the reason why the default configuration in a BLU-800 uses more DSP resources than a BLU-160. CobraNet has 32 channels, all of which are being fed in to the DSPs, therefore 32 of the 128 BusRx Ports to the DSP are already being used. You could still have a 128x128 matrix in a BLU-800 if the CobraNet was being fed in to the matrix along with 96 channels of BLU link.
The above all assumes running at 48kHz. At 96kHz, the number of BusRx and BusTx Ports are halved.