CPU Usage, Safe limits and Longevity

Hey guys,

Just wanted to clarify a few things about CPU usage...the manual states that the max allowed is 90% and while that seems to be the upper limit I'd like to know how safe it actually is to be pushing close to that? To be clear, when I say safe I mean both in terms of audio quality and the health and longevity of the hardware itself.

My patches typically tend to stay between 70-75% but I've been trying something new with dual amps (and therefore extra effects) that gets up to around 83-85% - is this too high to run as my main patch? I'm not getting any warnings but that friendly little meter in the top right corner of Axe-Edit has start tickling the reds just a bit and I want to make sure I'm not pushing the Axe too hard...
 
Running the CPU harder will not wear it out quicker.

Each little transistor on the chip can only do 1 thing at a time, they don't get stressed.

If the patch works fine, use it - the Axe is pretty good at warning you, and there's lots of tricks to reduce usage (only using 1-2 IRs, using the pre-amp boost rather than a drive pedal etc)
 
Just be aware that CPU usage can vary with firmware versions, so having a main patch close to the limit can mean that you have to tweak it if the next firmware version uses more CPU on some blocks (as they tend to do over multiple releases). My guitar and vocal patch needed redoing after 12.02, so Ive now put some vocal processing duties to outboard gear to reduce what the AXE FX needs to do.
 
A key point to note is that the CPU meter is only providing a status for 1 of the 2 cpus in the Axefx3. The other cpu, is, as I understand, is dedicated to Amp blocks, modifiers, and system functions.

My dual amp presets with moderate # of modifiers are pushing the limits of the amp side cpu (detecting digital clipping). See post here for more info including a sample preset which clips significantly with visible cpu showing only 25%.

I feel that the Amp side cpu needs a meter as much as, or possibly even more than, the Fx side cpu (I logged a wish for that which I hope can be implemented at some point).

I don't think high cpu levels are bad for the unit as long as fans are running properly to cool hot running cpus. What I find challenging is that clipping from high Cpu can creep in very gradually starting with very intermittent pops/crackles and progressing to a more constant "crackle".

For amp side cpu management, when using 2 amp blocks, items that seem to add to cpu usage include:
  • amp compression.
  • # of modifiers.
  • amp trem
  • amp graphic eq
  • amp type selected.
 
Make a preset that goes over 90%. You’ll see that the screen and controllers slow down, and there can be audio glitches. It’s not really about “safety” for the unit but usability at the performance.
Running the CPU harder will not wear it out quicker.

Each little transistor on the chip can only do 1 thing at a time, they don't get stressed.

If the patch works fine, use it - the Axe is pretty good at warning you, and there's lots of tricks to reduce usage (only using 1-2 IRs, using the pre-amp boost rather than a drive pedal etc)

Ok gotcha - so as long as I'm below 90% and everything is working fine it's 'safe'?
 
A key point to note is that the CPU meter is only providing a status for 1 of the 2 cpus in the Axefx3. The other cpu, is, as I understand, is dedicated to Amp blocks, modifiers, and system functions.

My dual amp presets with moderate # of modifiers are pushing the limits of the amp side cpu (detecting digital clipping). See post here for more info including a sample preset which clips significantly with visible cpu showing only 25%.

I feel that the Amp side cpu needs a meter as much as, or possibly even more than, the Fx side cpu (I logged a wish for that which I hope can be implemented at some point).

I don't think high cpu levels are bad for the unit as long as fans are running properly to cool hot running cpus. What I find challenging is that clipping from high Cpu can creep in very gradually starting with very intermittent pops/crackles and progressing to a more constant "crackle".

For amp side cpu management, when using 2 amp blocks, items that seem to add to cpu usage include:
  • amp compression.
  • # of modifiers.
  • amp trem
  • amp graphic eq
  • amp type selected.

Yeah that's interesting - is there any way to monitor it at all, or is this something that you either just hear or you don't and it's fine?
 
Ok gotcha - so as long as I'm below 90% and everything is working fine it's 'safe'?

Absolutely - honestly as long as the fans are running fine, even over that is safe.

But in terms of patches and knowing they'll work - 70-80% (which is a monster, monster patch let's be honest - I'm running two delays, two reverbs and a bunch of effects and I'm way under that) is fine
 
it's a pretty rare case. that's why it's not shown. i wouldn't worry about it. just play guitar.

Not that rare if running 2 amp
blocks with a moderate amount of modifiers. Try the preset noted in the post I referenced above - it is not an over the top preset.

I'm surprised at the lack of concern for cpu levels on what is arguably the much more important cpu (the amp side one) while we take great care to stay well below the red line on the fx side cpu.
 
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Not that rare if running 2 amp
blocks with a moderate amount of modifiers. Try the preset noted in the post I referenced above - it is not an over the top preset.

I'm surprised at the lack of concern for cpu levels on what is arguably the much more important cpu (the amp side one) while we take great care to stay well below the red line on the fx side cpu.
I've seen you post about this issue in various threads but I haven't really seen others posting the same issue (that I can remember).

Do you have corroboration from Fractal that your issue is what you think it is?

Do you have modifiers on the Amp block, or is it just modifiers in general?

Being that I've experienced slow/lagging modifier response on CPU heavy presets with only 1 Amp block, it's surprising to think the modifiers are being handled by the same CPU that's doing the amp modeling.
 
I've seen you post about this issue in various threads but I haven't really seen others posting the same issue (that I can remember).

Do you have corroboration from Fractal that your issue is what you think it is?

Do you have modifiers on the Amp block, or is it just modifiers in general?

Being that I've experienced slow/lagging modifier response on CPU heavy presets with only 1 Amp block, it's surprising to think the modifiers are being handled by the same CPU that's doing the amp modeling.

Hey

I've not had any feedback on this issue from Fractal.

My understanding of this issue is based on the testing I've done - since there's no visibility on the status of the amp-side CPU, it's all guess work really but I've narrowed it down quite a bit. See the attached simple preset which digitally clips for me. Note the following:
  • this is a more extreme example I made to confirm what is happening - usually what I've run into is just the odd pop / crackle here and there on duel amp presets - not a lot but enough to be annoying.
  • the digital clipping is not loud compared to the rest of the signal - the clipping is small pops and crackles you have to listen for through the distorted tone in this example (or you can turn the amps off and it will still clip on the clean thru signal).
  • you have to play for a minute or so to get the clipping started.
  • it happens more with Axe Edit open, but still does it without AxeEdit running.
  • it seems to happen more, the more modifiers you have, and the more you exercise them (there are 9 modifiers in this example).
  • it only seems to happen when running 2 amp blocks.

I'm looking for someone to corroborate if this example preset is doing the same thing on their Axe III in the latest FW.

Mainly I want to confirm there's nothing wrong with my unit - I don't think there is as there are no other issues occurring or signs of issues. I'm pretty sure I'm just clipping the amp side cpu (hence the wish for an amp side cpu meter). I agree it's odd no one else is running into this (that has me a bit worried something is wrong here). That's why I'd like to get others' feedback on the attached preset.

If it's not a problem with my unit and I'm just hitting the amp-side CPU limit I'd like to get a better handle on where that red line is and how to avoid it if possible. If it turns out we can get the amp side cpu clipping with reasonable presets then I'm hoping we can get the ability to balance amp blocks across cpus at some point.
 

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  • AMPSIDE-CPU-CLIPPING-B.syx
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Hey

I've not had any feedback on this issue from Fractal.

My understanding of this issue is based on the testing I've done - since there's no visibility on the status of the amp-side CPU, it's all guess work really but I've narrowed it down quite a bit. See the attached simple preset which digitally clips for me. Note the following:
  • this is a more extreme example I made to confirm what is happening - usually what I've run into is just the odd pop / crackle here and there on duel amp presets - not a lot but enough to be annoying.
  • the digital clipping is not loud compared to the rest of the signal - the clipping is small pops and crackles you have to listen for through the distorted tone in this example (or you can turn the amps off and it will still clip on the clean thru signal).
  • you have to play for a minute or so to get the clipping started.
  • it happens more with Axe Edit open, but still does it without AxeEdit running.
  • it seems to happen more, the more modifiers you have, and the more you exercise them (there are 9 modifiers in this example).
  • it only seems to happen when running 2 amp blocks.

I'm looking for someone to corroborate if this example preset is doing the same thing on their Axe III in the latest FW.

Mainly I want to confirm there's nothing wrong with my unit - I don't think there is as there are no other issues occurring or signs of issues. I'm pretty sure I'm just clipping the amp side cpu (hence the wish for an amp side cpu meter). I agree it's odd no one else is running into this (that has me a bit worried something is wrong here). That's why I'd like to get others' feedback on the attached preset.

If it's not a problem with my unit and I'm just hitting the amp-side CPU limit I'd like to get a better handle on where that red line is and how to avoid it if possible. If it turns out we can get the amp side cpu clipping with reasonable presets then I'm hoping we can get the ability to balance amp blocks across cpus at some point.
When I get some time I can try it out.

Just to be clear though, the term "clipping" usually refers to overdriving the output signal.

Digital clipping is a very harsh, nasty sound. Cracks and pops are (to my mind) not clipping. I've experienced those... I would call them "unwanted artifacts" (or just pops and crackles ;))

You can't clip a CPU as far as I know...

I think I know what you're saying, and it's mostly semantics, but just trying to make clear that we're talking about the same thing.

Edit:

Can you load the preset on AxeChange so I can load it with FracPad? I can't get it to work from download...
 
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When I get some time I can try it out.

Just to be clear though, the term "clipping" usually refers to overdriving the output signal.

Digital clipping is a very harsh, nasty sound. Cracks and pops are (to my mind) not clipping. I've experienced those... I would call them "unwanted artifacts" (or just pops and crackles ;))

You can't clip a CPU as far as I know...

I think I know what you're saying, and it's mostly semantics, but just trying to make clear that we're talking about the same thing.

Agreed - need to be clear
on terminology:

- This is not output clipping - it is cpu clipping which manifests as pops and crackles when cpu is getting too high. I've owned 2 previous axefx units (ultra,II) and they sounded the same when the cpu ran too high (too many blocks/ modifiers getting cpu into the mid 90s+). In Axefx III, for the fx side cpu, the unit will not allow you to add enough blocks to redline the cpu the way you can on earlier Axefx models, but for the Axe3 amp side cpu I'm pretty convinced I'm hearing the result of a red lined cpu (I'm calling this cpu clipping).

The thing with cpu clipping is that it can start very subtly at lower cpu levels - just the odd pop here and there which increases in numbers as the cpu level rises more into the red / this is likely why the fx side cpu monitoring is set up to start warning at 80% - it's a gradual thing that starts small and increases (though small could be a showstopper in a pro studio).

Anyway - try the preset.

Also - fyi - I've confirmed this through headphones also which I think eliminates the possibility there's an issue at the external output.
 
The cpu readout is only showing a status on 1 of the 2 cpus (the fx side cpu). The amp side cpu status is not visible - hence the discussion here, and wish to have an amp side cpu status meter.

I'd post the suggestion in the Wish section. If enough people want it they might add it.
I'm happy as it is, but I can see how it might be useful.
 
Absolutely - honestly as long as the fans are running fine, even over that is safe.

But in terms of patches and knowing they'll work - 70-80% (which is a monster, monster patch let's be honest - I'm running two delays, two reverbs and a bunch of effects and I'm way under that) is fine
it's a pretty rare case. that's why it's not shown. i wouldn't worry about it. just play guitar.
I keep presets under 85%. Most of mine are about 76-80%. There's a lot of info on the wiki about CPU usage.

http://wiki.fractalaudio.com/axefx2/index.php?title=CPU_usage

Good to hear all this...yeah it is a monster patch so I just wanted to make sure I wasn’t screwing anything up :)
 
And @sprint re your dual amp issue...not sure what’s going on there but I tried your patch and it’s like someone’s making popcorn. Has this happened to you with other patches?

My dual amp situation is completely fine and I’ve never had an issue like this...
 
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