Ableton Forum

never noticed this before so might be a 8.2.8b issue...

i've got 4 instances of the vst synth Aalto running on seperate tracks. the cpu is a steady 24%,
but if i put those same 4 Aalto instances into a single instrument rack and disable the ones on their own tracks, the cpu doubles. same sounds, same number of plugins enabled.

also just tested with a bunch of Operator presets (5 of), all on seperate tracks and playing at once, then the same presets but put in an instrument rack and played at once.
same thing happens to cpu: non-racked = 6%, racked = 13%

has this always been the case and i've just not noticed before

mbp quad i7

Is it possible that you need to remove and not disable the plugs that are not in use?

Try it.

I wonder if the fact you have them in a rack means that that entire rack is processed on a single core and when on different tracks, each instance can be processed on separate cores? I know this was an issue with Kontakt when you send multiple outputs to several effects busses - all are assigned to the same core. I don't know if this is the reason - just a thought....

Rinsemeister wrote:Is it possible that you need to remove and not disable the plugs that are not in use?

Try it.

nope. besides, its not about not having the cpu spare. i have plenty. this is about racks taking up twice the cpu of equivalent seperate tracks.

try out this .als - its just a bunch of home-made presets stacked to have a noticeable impact on the cpu:
http://dl.dropbox.com/u/78200/operator%20cpu%20test.als

i've mapped the qwerty keys 1 & 2 to flip between monitoring the rack and the separate tracks.
hold down a midi note and note down the cpu hit. then wait for the release tail to die out and the cpu drop to 0, and flip to the rack. note the cpu.

here the results are:
grouped operator tracks = 6-7%
racked operators = 13-14%

trevox wrote:I wonder if the fact you have them in a rack means that that entire rack is processed on a single core and when on different tracks, each instance can be processed on separate cores? I know this was an issue with Kontakt when you send multiple outputs to several effects busses - all are assigned to the same core. I don't know if this is the reason - just a thought....

i think you could be right. a glance at the activity monitor in osx seems to show this. does Live actually report its cpu usage across all cores, or just one, and adjusts as one core 'fills up'?

garyboozy wrote:i think you could be right. a glance at the activity monitor in osx seems to show this. does Live actually report its cpu usage across all cores, or just one, and adjusts as one core 'fills up'?

I don't know to be honest, but I would think the CPU meter shows the core with the most usage as that would kind of make sense. I wish there was a similar meter to Logic which shows usage in each core - would help a lot in figuring out things like this!

yea would be handy to see the cpu usage per core from within Live.

still the same in 8.2.8b3

confirmed by support. they even told me the same was true in Live 7.0.18 and that it would be looked into.
but if it's gone this long without being flagged, i doubt it'll be fixed.

Thought that might be the case. Guess the only workaround is not to create racks. Similar to how I had to use multiple instances of Kontakt where I could have done it a lot easier using one with multiple outs.