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Amp Block and Effects DSP Percentages


It may be a bit early to be asking this question, but I am curious if anyone has begun to look at amp and effects drain on DSP. I know that on the II there were a couple lists that users had published at different points in the firmware history that would give you a good idea of what you could fit into a preset. I was also wondering if @FractalAudio or anyone could answer if the DSP use is divided up in a similar fashion as the II, with one DSP handling amp blocks only (more or less) and the other dedicated solely to effects. Would any new owners care to share any insights? I expect it will be quite a few months before I get my purchase invite, but it's never too early to start planning! ;)

Jack Napalm

Power User
I recreated a basic patch I use on a II. The II has CPU at 44%. The same patch on the III is at 27.5. Remember that with the III I don't have a lot of shunts.

The patch is Input -> Wah -> Drive -> Amp -> Cab -> 2 Delays in Parallel -> Output


Fractal Audio Systems
Also on II the CPU usage increases when you play whereas on the III it more or less stays constant.


I've been recreating all of my patches. It looks like a lot of the patches that were at 80% on the II (idling, not playing) are now at 60% on the III. That's just quickly skimming through the patches and eyeballing it.


Fractal Fanatic
I mentioned it elsewhere, but I have never seen this low of CPU usage on any Axe FX device. Cooper's "Petrucci Rig" with a full compliment of normal blocks, second input for the piezo pickups on the Majesty, and 8 scenes pulls a whopping 50.6%! I'm not going to say someone here won't hit the wall, but I honestly can't see myself ever doing it in normal use.


Power User
I had to get pretty creative with adding a LOT more than I would ever need in a preset in order to find the limit. Just about 1 of every type of modulation, normal delay, plex delay, reverb, ring mod, wah, comp, full cab with all 4 enabled. I think it finally cried uncle when I added a second pitch to try to do a whammy pedal.

And no, I didn't save that preset. I'd never use most of the stuff in it. Just had to see how far it would go.


Chris, does adding 2./3./4. IRs in Cab block change the CPU or Memory usage?
Yes. When a Cab Slot is Muted, it is not using CPU. Unmute and it begins processing. Note that this isn’t something you can mute/unmute with modifiers. These are slots within the Cab block itself. You can change Channels for different arrangements though.


FWIW, when I add a second Amp block to a preset, CPU usage goes up by a whopping ½ percent. ;)
This would indicate to me that one DSP is handling the amps, same as on the II. What we don't know is if that DSP can handle effect also if an amp block is not in use. I would say probably not, otherwise DSP use would show higher on the meter when an amp block is engaged. So the 100% you see available on an empty preset is really only about 50% of the available power on the device. It seems like it might be nice to have access to it if you weren't using it for an amp block, but it might not be technically feasible, and it might be overkill anyways.
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