When Live 6.10 or 7.01 are running under Windows Vista (SP1 RC) using the Basic Desktop (aka Classic Desktop) then CPU load increases dramatically (can increase well over three times of the original CPU load). This does not happen when Vista's Aero is used, which on my system increases CPU load only by an average of about 2% compared to Windows XP.
This bug is only related to Live's GUI drawing but I cannot say wether it's a bug in Live or a bug in Windows Vista. The ammount by which CPU load increases depends on what GUI elements are displayed by Live. The increased CPU load can be reverted to normal by sending Live to background and then changing screen resolution or screen refresh rate! But as soon as Live's window is displayed the CPU load will increase above normal again.
Here some examples (Audiophile 2496 using 512 sample buffers):
Tarekith Performance Test
Windows XP
Live's meter: 52%
Task-Manager: 55%, 51% when running in background
Windows Vista Basic Desktop (NO Aero)
Live's meter: 53%
Task-Manager: 77%, 52% when running in background after resolution change
128 concurrent samples through a Drum Rack track (1 bar), Task-Manager Process list CPU load
Windows XP
All views including running in background: about 16% (regardless of Midi port activation as it seems)
Windows Vista Basic Desktop (NO Aero)
Midi Clip View: 42%
Drum Rack View, chains hidden: 50%
Drum Rack View, chains displayed: 53%
Empty Track, no instruments/effects: 33%
Running in background (no GUI displayed): 33% background
Turning on any Midi ports increases load by appr. 3%.
Running in background (after changing resolution): 16% (regardless of Midi port activation as it seems)
This bug is independent of Windows' DPI settings. The latest NVidia driver was used for my 7800GT. I will try to use uninstall the drivers and use the shipped one and I will also uninstall SP1 RC to make sure those two are not to blame for the situation. Tarekith reported similiar figures and returned to Windows XP because of this, so it's not only happening on my computer. It happens with all three of my audio-cards!
A64 X2 @ 2.83 GHz, 2gb RAM, NVidia 7800GT, Audiophile 2496, Creative X-Fi, NI Kore 1
DRAMATIC CPU load increase when using Vista Basic Desktop
Timur!
you are a legend!
recently I've been reporting that Vista is using WAY more resources (like 20-30%) than XP SP3 - and I was shocked by this
now because of you pointing this out I just tried Aero again and the CPU went down to almost on a par with XP
the file DWM.EXE that is inthe task manager when aero is running seems to consitantly consume CPU cycles, although it is only 1-2%, but it also uses about 50MB of RAM - so I have been ending the process in task manager after finding it mentioned online - if you end it once it comes right back, but if you end it a second time then it stays gone and if you go back to your appearance settings (classic view) then Aero is no longer present and it is set to 'vista basic' , and the CPU consumption is wildly more than it is with aero
so it seems you have noticed a biggie here!
weird - I've been putting it on vista basic specifically to free up resources but it turns out it was having the opposite effect
I actually like vista but the performance is a big deal - I will see how I go now with Aero
of course even with Aero enabled you can still disable some resource consuming effects such as transparency
I have been having different problems in XP - for some reason I've been getting a sudden buzzing on the input with my FW410 that requires me to turn audio off then on again in Live - but it's not a Live bug because Reaper does it too
it never used to happen on my old computer, but I think because this laptop was intended to have Vista then the XP drivers are not the best for some of the components - and maybe the FW bus is one of them
so if I can get better performance in vista then great!
thanks Timur - you are the uber tester!
you are a legend!
recently I've been reporting that Vista is using WAY more resources (like 20-30%) than XP SP3 - and I was shocked by this
now because of you pointing this out I just tried Aero again and the CPU went down to almost on a par with XP
the file DWM.EXE that is inthe task manager when aero is running seems to consitantly consume CPU cycles, although it is only 1-2%, but it also uses about 50MB of RAM - so I have been ending the process in task manager after finding it mentioned online - if you end it once it comes right back, but if you end it a second time then it stays gone and if you go back to your appearance settings (classic view) then Aero is no longer present and it is set to 'vista basic' , and the CPU consumption is wildly more than it is with aero
so it seems you have noticed a biggie here!
weird - I've been putting it on vista basic specifically to free up resources but it turns out it was having the opposite effect
I actually like vista but the performance is a big deal - I will see how I go now with Aero
of course even with Aero enabled you can still disable some resource consuming effects such as transparency
I have been having different problems in XP - for some reason I've been getting a sudden buzzing on the input with my FW410 that requires me to turn audio off then on again in Live - but it's not a Live bug because Reaper does it too
it never used to happen on my old computer, but I think because this laptop was intended to have Vista then the XP drivers are not the best for some of the components - and maybe the FW bus is one of them
so if I can get better performance in vista then great!
thanks Timur - you are the uber tester!
I am seriously considering to ask Ableton for a free version of Live 7 for all the time and effort I have spend in finding their really hard to find low level bugs! Being a computer expert I usually get paid for this kind of work! 
I have done in-depth testing using Tarekith' Performance Test. But instead of having only 8 tracks run I tested how many tracks of Tarekith' test I can run concurrently with both my Audiophile and X-Fi in Windows XP and Vista Basic/Aero.
Result: Audio performance is basically the same for all settings!
But when using Vista Basic Live's GUI get's choppy really quick and very obviously is the reason for Live's high CPU load under this setting. When using Aero the GUI stays fluent until CPU load by the audio-engine gets into its way just like with Vista.
When using Aero you need to make sure your audio-interface does not share its IRQ with your graphic-card, because Aero uses 3D functions which in turn use the graphic-cards IRQ. Graphic-card IRQ is usually not used in 2D, regardless of wether you're using XP or Vista, so it doesn't really matter if they share IRQs when staying in 2D.
When doing performance tests/measuring CPU load using Task-Manager make sure to change Task-Managers priority to at least "Normal", better to "Idle". The default priority of "High" will lead to drop-outs even if you set task-managers refresh-rate to low. This does not happen under XP, so either Task-Manager uses more resources or the ASIO driver use a lower priority than in XP (I fear for the latter).
I have done in-depth testing using Tarekith' Performance Test. But instead of having only 8 tracks run I tested how many tracks of Tarekith' test I can run concurrently with both my Audiophile and X-Fi in Windows XP and Vista Basic/Aero.
Result: Audio performance is basically the same for all settings!
But when using Vista Basic Live's GUI get's choppy really quick and very obviously is the reason for Live's high CPU load under this setting. When using Aero the GUI stays fluent until CPU load by the audio-engine gets into its way just like with Vista.
When using Aero you need to make sure your audio-interface does not share its IRQ with your graphic-card, because Aero uses 3D functions which in turn use the graphic-cards IRQ. Graphic-card IRQ is usually not used in 2D, regardless of wether you're using XP or Vista, so it doesn't really matter if they share IRQs when staying in 2D.
When doing performance tests/measuring CPU load using Task-Manager make sure to change Task-Managers priority to at least "Normal", better to "Idle". The default priority of "High" will lead to drop-outs even if you set task-managers refresh-rate to low. This does not happen under XP, so either Task-Manager uses more resources or the ASIO driver use a lower priority than in XP (I fear for the latter).
I only got this message when switching display resolutions while having opened Live under Aero. I have no problems opening VSTs or the manual. Try switching all visual effects in Windows off, except (don't know the corrent english names):
Activate Desktop Designs (? it's "Gestaltung" in german)
Visual Styles for Windows and blabla
Both of these are needed for Aero to work. Most likely you will also want to use Cleartype, no idea how this option is called in the english versions. It shouldn't matter wether you use the Glass option or not.
Could an Ableton technician care to acknowledge this bug please? If not then I will send it via mail to the support, because I think that this is a mayor bug that keeps some people from properly using Live at all.
Activate Desktop Designs (? it's "Gestaltung" in german)
Visual Styles for Windows and blabla
Both of these are needed for Aero to work. Most likely you will also want to use Cleartype, no idea how this option is called in the english versions. It shouldn't matter wether you use the Glass option or not.
Could an Ableton technician care to acknowledge this bug please? If not then I will send it via mail to the support, because I think that this is a mayor bug that keeps some people from properly using Live at all.
One definite source of the problem is Simpler. Even when not in focus (Live showing another empty track) triggering Simpler increases CPU load considerably. When in focus a single Simpler playing a single Sample note can easily consume more than 50% on my X2 2.83 GHz CPU. The longer the note/release the higher the CPU load. As soon as Simpler is disabled CPU load drops alot (though still a few single percents higher than it should be).
I did find out that Simpler forces my Nvidia 7800GT into high clock-rate 3D performance mode when the card's 2D mode GPU is clocked somewhat below 250 MHz. This usually doesn't even happen when using Vista's 3D task-browser and even if it happens from time to time the card will drop back to low power mode after only a few seconds. With Simpler running the graphic-card stays under heavy load. The bad thing about this is that even when CPU load stays relatively normal with Aero enabled the GPU remains heavily loaded. It's even so graphic intensive that running Tarekith' performance test shows different CPU load results depending on the clock-speed of the GPU!
I mean, ok, Call of Duty 4, yeah, heavy duty for both GPU and CPU, but Simpler? Did I miss the feature 3D power-game easter-egg somewhere in it? Whatever function-calls Ableton is using for Live's GUI there is something fundamentally wrong with it when it's being used in Vista. Again, if no one from Ableton acknowledges to have read this thread I will post all this in an e-mail to make sure it reaches your attention. This is such a bad bug, that you either have to solve it quickly or delete the line "Windows Vista" from the stated System Requirements. Did anyone even test it with Vista before (a suitable question given the very obvious nature of this bug)?
I did find out that Simpler forces my Nvidia 7800GT into high clock-rate 3D performance mode when the card's 2D mode GPU is clocked somewhat below 250 MHz. This usually doesn't even happen when using Vista's 3D task-browser and even if it happens from time to time the card will drop back to low power mode after only a few seconds. With Simpler running the graphic-card stays under heavy load. The bad thing about this is that even when CPU load stays relatively normal with Aero enabled the GPU remains heavily loaded. It's even so graphic intensive that running Tarekith' performance test shows different CPU load results depending on the clock-speed of the GPU!
I mean, ok, Call of Duty 4, yeah, heavy duty for both GPU and CPU, but Simpler? Did I miss the feature 3D power-game easter-egg somewhere in it? Whatever function-calls Ableton is using for Live's GUI there is something fundamentally wrong with it when it's being used in Vista. Again, if no one from Ableton acknowledges to have read this thread I will post all this in an e-mail to make sure it reaches your attention. This is such a bad bug, that you either have to solve it quickly or delete the line "Windows Vista" from the stated System Requirements. Did anyone even test it with Vista before (a suitable question given the very obvious nature of this bug)?