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Some background info:

I'm a .NET developer working on a Dell Precision M4500 notebook (i7 X 940 @ 2,1 | 8GB DDR3 | Details). Tools I use on daily basis (and which are basically open the whole work day): two instances of Visual Studio 2012 (+ Windows Azure Emulator), Chrome with several Tabs, TortoiseHg (version control tool), Outlook, Skype -> Normal setup nothing special I think.

Stats during normal use:

Avg. CPU load: 15-20%. Avg. Memory: 2-3GB (30-40%)


Several weeks ago we (two coworker and me, all with the same notebook model) moved from Win7 to Win8 (fresh install -> no upgrade), since then I'm encountering some performance issues. From time to time (mostly, but not always after building and running our application) my notebook is barely usable for several minutes -> UI extremly slow or doesn't respond at all. Even after I stop the debugging session, notebook is extrem slow. After a few minutes, CPU load goes done and I can continue working.

Stats during performance peak use:

CPU load: 56%. Memory: 5-6GB (60-70%) Also high read/write activities on C:\pagefile.sys according to ResourceMonitor (I guess that's normal?).

First strange thing: the max. CPU Utilisation never exceeds 56% (none of the CPU goes over 56% see picture below).

CPU Utilisation

Second strange thing: only my notebook is experiencing those performance issues.

Things I've tried:

I've already installed latest driver for graphic card (NVIDIA) and intel chipset. Also compared my notebook with the coworker notebooks -> same software, same driver, same project setup, no greater differences. Installed and run the Intel Processor Diagnostic Tool -> Passed. Also no defect or error on the RAM.

And yes, I also checked the power settings (I'm using High performance), the maximum processor state is set to 100%.

The Question:

I know nobody can tell me the exact cause of this specific problem.

But my question is, why is the CPU load never exceeding 56%? Where does this strange limitation come from?

Maybe solving this mystery will bring me a step closer to the solution of the performance problem.

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I had almost the same problem when I decided to try to work on Win8, after few hours I decided it`s easier to go back and again use Win7 without any problems. – Nidzaaaa Mar 6 '13 at 15:14
Check this link: Maybe you can find an answer. – Nidzaaaa Mar 6 '13 at 15:16
@Nidzaaaa and Griffin: Unfortunately I can't go back to Win7, we are using WebSockets (.NET 4.5) which are not natively supported under Win7 (…). – Robar Mar 6 '13 at 15:20
Have you tried forcing it to go over the 56% limit by using a benchmarking or "burn-in" program (like Prime95)? – techturtle Mar 6 '13 at 15:31
But have you tried to open Task Manger (or Resource Monitor) and sort processes by CPU utilization to see which processes are actually responsible to slowing down your computer? – Desmond Hume Mar 6 '13 at 16:01
up vote 1 down vote accepted

After additional research (BIOS diagnostic test), I discovered that the temperature of my CPU was at 80°C (GPU @ 75~80°C).

So I thought maybe some cleaning would do the trick. I openend the Notebook (as described in the documentation of the notebook I found online @, disassembled the heat pipe and the CPU cooler fan and carefully cleaned them, put the things together and started the laptop. After five workdays my notebook works just fine, I think the overheating was the root of the problem. CPU and GPU are now @ 60-65°C.

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