Indeed, upgrading from 10.6.8 might not be a good idea for live users. I decided to give 10.8 a try when I bought a new SSD hard drive for faster boot up times. And for me, upgrading to 10.8 fixed all the weird midi issues I had with 10.6.8, forcing me to unplug and reconnect my midi devices and also to reboot way too often. With 10.8 they all work "plug and play"-way as I expect them to, so that's why I never went back to 10.6.8. Also audio works fine for me, as long as my battery level's not in between 75-95% and charging.  Rarely, but sometimes I do get dropouts with live even at full battery, but I hear it right away and closing and restarting live fixes this.

As for the battery management bug. I fear this might not be an ableton-only bug. But I haven't had the time to test with other processor hungry apps. It starts and stops immediately when the battery level reaches the percent limits, so I think this should be an easy fix for apple, if they just take this seriously. I'm sure someone at their end knows what exactly happens in battery management at these two percentage marks.

I also hope that the next week's Live 9 release (with 64bit support) will bring some improvements to live's cpu handling.

UUu yeah!! Thanks a lot for the tip! I hadn't noticed that, and of course it's good to try before buy. :-)
I still have to upgrade before next week to get the discount, but at least now I'll know beforehand if everything in my setup works.

I am currently trying to reproduce this on an early 2011 17" MBP (i7 2.1, 8 GB 1666 RAM), with no success yet.

Some questions: Does it make a difference whether you are disconnecting everything from your Mac, including external display USB device, UFX?

How is the UFX connected (Firewire or USB) and does that make a difference?

What is in your DVD drive bay, the DVD recorder or a second HD?

Does it help to raise the backside of your MBP up by placing something underneath it (watch out not to cover to much of the bottom plate and not to cover the air outlets at the hinge)? Try opening the screen just a hint further than 45°, but not much further and not less than 45°. The reports you linked to reported about a relation to heat, so my MBP is currently sitting on a cushion to help it heat up from loading the battery.

You wrote that you are using the internal Intel graphics, so I assume that Ableton Live is not running (it forces to use the dedicated GPU)?! What happens when you stop all applications (in combination with detaching all external devices)?

Install iStat Menu and take a look at its heat readings, which include current and max battery temps, plus the airflow temp around the DC in. Watch what happens with temps right before the battery reaches 75% and right before the CPU load increases. Also watch the amperages as reported by iStat.

One thing that comes to my mind is that the 75-95% range is special. Above 95% the MBP only load the battery once to 100% and then stops loading until it drops down below 95% again. This is in order to preserve battery life, as the last 5% produce the most heat. Regarding the 75% I can imagine that battery loading is successively slowed down from that point, something many modern loaders do in order to preserve battery life (heat) and keep the battery from melting down (not always successfully). I am currently measuring that.

Little busy now, but I'll try to test with the iStat menu during the weekend.

What I can answer right now:

-my UFX is always connected with firewire. (So much gear connected to USB already.)
-original dvd recorder inside, no mods there
-I've always kept my macbook raised a bit to let the air flow underneath, but I also just bought this cooler to go under it. Don't know if it will help, but it can't do any harm to try to keep things a bit cooler. The rack gear under my laptop (UFX, yamaha rack synth, and a couple of effects) do generate some heat as well.
-I've done a full battery unload, yes. I try to do it every once in a while.
-I do have an external display connected. (Only 1440x900 resolution, if I remember correctly. Lower than the internal "HD" display's resolution anyway, and I keep the display in mirrored mode) Actually I just wrote what hardware my macbook has. Forgot it has "two" graphic cards. I have to check my preferences to see which one is actually being used.. I haven't even thought of that. Probably using the separate graphics card anyway, I assume.

But I'll get back after testing some more..
Thanks to you for testing also!

All right.. I did 4 tests today measuring with istat menus, and taking lots of screenshots.

It appears that this might indeed be a heat issue, but also a combination of other things. Let me know what you think.

all the screenshots are here: (about 75mb zip file. Sorry, I didn't have the time to take off unnecessary images or make them smaller)

-----------
The 1st test was done the way I've set up normally:
-FW connection to UFX,
-Ableton Live 8.3.4,
-External display connected in mirror mode (both screens at 1440x900 resolution)

I started Live, played something in, and kept live looping after that. I let the battery drain down to 66% before connecting to (85w magsafe) charger. CPU usage (ableton cpu meter) stayed at about 25% all the time. At 18.46, I connected the charger and at first things were running smoothly, - you can see the battery meter is calculating the charge up time, at 18.49 showing 6:31h charge up time, and everything is still ok. At 19.00, only 10 minutes later you can see the battery charge up time is down to 1:20h, so it's charging faster, and that's when the trouble started! (anything above 50% = trouble expected) Just look at the cpu meters.

I then disconnected my external display at 19.01 (all the higher resolution images with ableton window not taking up all the space, are taken when external display is disconnected) And the cpu levels started dropping. They didn't go as low as they should (normally 19-21%) and instead kept at around 30-40%.

Then reconnected the external display and cpu usage started rising again.
The heat is not changing that much, so I think the problem might be simply related to power usage. But again, I'm really not an expert so hopefully someone with better knowledge can step in..

At 19.35, I disconnect the power adapter. CPU usage drops immediately down to 25%!!!

19.37, - connect to power again, and CPU starts rising..

Rest is pretty much the same. Disconnecting the display a couple of times, and just saving readings.

After 95% capacity, the cpu meter stays at around 30%. Still actually a bit more than usually, but acceptable anyway.
-------------------------------

The 2nd test was done with UFX connected via USB. Really no difference there.
Just watch when the battery is charging, when disconnected from power, and when using the internal display only.

---------------------------------

The 3rd test was done with USB connection, but using Live9 Beta (64bit) instead.
The problems remained, but the CPU usage didn't go just as high.
Also the idle (not playing) CPU usage is down to 10% instead of 20%. So some improvement there.  Just a short test here.

-------------------------------------

The last test was done with the laptop cooler and spinning fans under my macbook. Settings were the same as in test no.1.

NOW THIS IS HOW IT SHOULD BE! cpu meter at 20% all the time, even when charging.
I guess the cooler does something. But honestly, to me it looks that the heat difference is not that big. Even the laptop fan speed is pretty much the same as in other tests. But I guess it's just enough to keep things running.

Without the cooler, I was able to keep things running somewhat ok with the external display, by using
nosleep extension, that allows me to close my macbook lid and internal display, while keeping external display running. However, I often need to access my laptop display, keyboard and mouse too, so this is just a bad backup solution for me.

I still think I should blame the 10.8 power management for this issue. I had my macbook on the very same rack when using 10.6.8, and everything ran ok there. The os x should be able to keep things running smoothly - and simply charge the battery slower if necessary! Or there should be some software to disable charging, when computing power is really needed.

I'm tired, probably unclear with my writing, and need to go to sleep now. Hopefully you can still find some info from this post.

Good night!

I actually need to have the same content on the two displays, so that's why I run them mirrored.
(One reason is that I have programmed mouse movements and clicks to do multiple tasks for me quickly in between, and in the middle of songs. And they depend on the resolution of the screen to hit the right spot)
1440x900 is the native resolution of my external display, and when connecting, os x just drops the internal display to that resolution too.

I tried the systemload, but results were more or less the same as in my first test. At first it seemed a bit more stable, but when the problems kicked in, they kicked in again. Cpu didn't go all the way up to 100% this time, but problems were the same anyway.. So after battery starts loading more intensively, the cpu meter starts rising. A good indicator for me is when my programmed keypress combos start to slow down. Then I know that audio drops will happen soon too.

No you didn't miss. I forgot to mention it. Unplugging USB devices does nothing, unplugging external display drops cpu a bit, and unplugging UFX (disconnecting ableton audio device) drops cpu to normal idle levels. Also quitting ableton drops the cpu usage to normal idle levels.

Yes it does. I quitted ableton, rebooted (actually had somekind of a crash while rebooting.. report here) Then started ableton again, and cpu meter jumped right up to over 80%

I quickly took my MBP to a local apple repair last friday, and they did some kind of a quick test and said that the communication between mac and the battery should be fine. However I might take this back for them to do some more testing..

Well ableton live is the one software I've been testing with. And I also know how live should behave.  (I said I fear this might not be an ableton-only bug, but I really don't know.) I tried rendering with final cut pro, and the cpu is up to 100%, but I don't know how that software is supposed to behave. Maybe it's ok to have it render with 100% cpu usage. No need to perform or worry about audio cut offs while rendering. On apple support communities discussion people don't mention the apps they're using, so I assumed this might be a more universal problem and not exlusively an ableton issue.

But that's right, my post was all along about problems with cpu usage while using ableton on 10.8.2.

Cool, thanks a lot for your trouble!

Hi Timur, and sorry for the delay.

I tried to determine whether my 10.8.2 uses 32 or 64 bit kernel. (my system is in finnish, but in system info -> software, it only says something like "boot state: normal" nothing about 32 or 64bit. So where to find this info?

On this apple support page they say that "If you are using OS X Mountain Lion, switching to a 32-bit kernel is not supported. Mountain Lion uses 64-bit mode."

In iddle mode the cpu usage is naturally down do decent percentages. What set I'm running doesn't matter. Can you try to reach the 20% cpu usage (live's cpu meter) somehow? Play some audio, have some effects on tracks and drop the sample buffer down to get cpu high enough. 20% is the normal cpu usage in my sets when playing. And it stays steadily there unless I'm charging..