I realize the codecs don't do any processing, that's not what I was thinking of. I was thinking that maybe one DSP might be handling the EQ routing, (Pre and Post Distortion) as well as the Cab sims since that is also EQ related. It may also be where it sets up the circuit path for the particular amp you've selected.
In your earlier post, you said the signal goes into the 1st codec from the Trim pot which makes sense, since that is supposed to be where you set the level of the guitar before analog to digital conversion. Then, it comes out of that codec and into the tube section, which is where you adjust your gain level according to the amp type, (and gain threshold), you selected. Then it goes to another DSP from there, by way of another codec, which I'm guessing would be where the effects are in the circuit path before going to the poweramps.
I'm also reasonably certain that one or both of those DSP's have something to do with the utility controls in this amp as well, meaning the MIDI data, CC functions, expression pedal, and recording outputs, programming assignments, etc.
These amplifiers do a lot. Either way, whether these amps are typical modeling amps or a more complex version of a modeling amp, they still sound great, and I wouldn't be afraid to put either one of these rigs next to any tube amp rig and let it rip.