GPU tasks use 50%+ CPU?

I'm running the GPU tasks with application ...0.82 (ati14) on a 3850.
They regularly eat +/- 50% CPU of my Gallatin at frequest, sometimes prolonged bursts.

I have the CPU usage set at a default of 10%

Why are these GPU tasks noticably eating CPU power?
Why are these tasks using 5 times my CPU usage limit?

I have a similar System to your's. But I work with an app_info.xml
that turns of the checkpointing witch can be reponsible for the CPU load during the WU.
At the end of a WU the CPU has to do some work(aboout 5 - 10 seconds). This is done in a bulk, and doesn't care about the CPU settings for CPU-WU's.

<app_info>
<app>
<name>milkyway</name>
</app>
<file_info>
<name>milkyway_separation_0.82_windows_intelx86__ati14.exe</name>
<executable/>
</file_info>
<app_version>
<app_name>milkyway</app_name>
<version_num>82</version_num>
<flops>1.0e11</flops>
<avg_ncpus>0.05</avg_ncpus>
<max_ncpus>1</max_ncpus>
<plan_class>ati14ati</plan_class>
<coproc>
<type>ATI</type>
<count>0.5</count>
</coproc>
<cmdline>--gpu-target-frequency 120 --gpu-disable-checkpointing</cmdline>
<file_ref>
<file_name>milkyway_separation_0.82_windows_intelx86__ati14.exe</file_name>
<main_program/>
</file_ref>
</app_version>
</app_info>

Fixed - apparently it was the (old) Catalyst drivers that I had. They also caused results to be invalid - see seperate thread.
Now running 11.8 (AGP) and things now seem OK.

Question for you - where do I get the info-app.xml file for milkyway?

I have one for Seti, but pretty sure it won't be something I can just copy over....

On Seti, I used it to set my GPU to .5, so I can process two tasks on the GPU at a time - can I do that for milkyway as well?

Even though my GPU does not run MW no DP, runs Collatz i have dedicated one core to GPU. GPU runs faster, cooler and much more happy and my RAC went up.