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So when I am doing something like calculating a file integrity hash, converting a video, compressing some files etc. why does my CPU not reach 100% usage, instead it happily jumps around from 0% to 15%. Now I appreciate that other things are going on and Window's scheduler cannot allocate 100% CPU to any one task, and some tasks are limited by other factors, such as waiting on the hard disk, network connection etc. and some tasks aren't suited to using all my CPU cores, is this poor coding (on application or OS)?. But instead of wasting these CPU cycles cant such tasks be sped up? I have an i7 Processor by the way, but am asking this question in general, rather than specific to my CPU.

Also why would my CPU ever be at 0% usage? Its always doing something right, or is this a rounding thing - as reported by Windows task manager.

Thanks

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It sounds like whatever tool you're using supports only one core. 1 core of 4 core with HTT is 12.5% CPU Max –  kobaltz Feb 19 '13 at 1:39
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2 Answers

12-15% is about the percentage you'll get when an application only uses 1 out of 8 cores on a i7 (4 cores + hyperthread), so it does seem like your applications are only using one core.

Most file hashings will only use 1 core to avoid overloading the disks. Many file and video compression softwares use multiple cores, but not all - what softwares are you using for converting and compressing?

As for the 0%, it's possible if few background processes are active. It could be very well oscillating between 0% and 1% when idle, thus showing 0 frequently.

I'm not seeing a problem with your situation, other than you are not using applications that support multiple cores where possible/applicable.

If anything, you should be able to run 2 of those tasks at the same time without any speed reduction, and a single task won't impair your ability to use the computer without hiccups.

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Also hyperthreading can create severe errors. So it won't use it. –  Griffin Feb 20 '13 at 2:05
    
@Griffin Care to explain or link to source? –  mtone Feb 20 '13 at 6:13
    
"It must be understood that not all Hyper-Threading performance problems are due to bugs. Hyper-Threading employs a number of tricks and compromises that can mean that it just isn't appropriate to use it in all scenarios. In some cases, systems can perform better with Hyper-Threading disabled. It is important to realise that many problems are not specific to Novell NetWare with Hyper-Threading. These are industry-wide issues, not just NetWare issues. These same types of problems could happen with any operating system that is running on hardware with Hyper-Threading capabilities." –  Griffin Feb 21 '13 at 0:49
    
This is best said by Novell novell.com/coolsolutions/feature/637.html –  Griffin Feb 21 '13 at 0:49
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mtone has provided a great answer.

I will add that if you've got a particular app that you feel really should be using more cores than it is, you may wish to consult your documentation to make sure you're using it in the most effective fashion.

There may be settings that would be better for your hardware and use case than the default. For instance, if you want to use the 7-zip file archiver application and make sure you use as many cores as possible for large jobs, you'd want to make sure you use the lzma2 algorithm when possible.

I also have an i7, and my experience is that our CPUs are almost never the bottleneck; in the vast majority of applications you'll hit limits associated with the speed of your disks, RAM capacity, or graphics processor prior to hitting the limits of your processor.

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