I have recently had fairly regular issues with the performance CPU meters spiking irregularly, along with audible pops/clicks.   I ran DPC latency check and it seems all ok, nothing wrong there - even when the spikes show in Sonar.   Current latency always well under 100us.
 
My PC is reasonably powerful (see signature), and I don't think I'm giving it too much work to do - mainly soft synths, perhaps up to 10 instances open, not all playing.
 
Any ideas what is most likely thing to check next?

Hmm,one would think a Xeon E5 1620 would be enough,however 10 softsynths is a lot for me,I'm more inclined to think it maybe a Windows optimization issue,though W7 does not need optimizing like XP did.
 
I have an i7 2600K OC'ed to 4.6GHz,and its never more than half[with the X3 "yellow bars"] though my soft synth use is fairly limited to drums,and far too many plugins,so I'm sorry to not be any real help,I just hope my post bumps the thread so you get some answers.
Bob

A lot depends on the soft synths. Some suck a lot more power than others. Also, what is your sample rate and number of sample buffers?

I have recently had fairly regular issues with the performance CPU meters spiking irregularly, along with audible pops/clicks. I ran DPC latency check and it seems all ok, nothing wrong there

 
You can have the best PC, but if you do not have your sound card drivers set up correctly for that Particular project, you can have CPU issues.
 
So make sure you have a good sound card with good drivers and are up to date..
Then Try each driver mode, ASIO and WDM with different buffer and slider positions to see what works the best for this project. 
 
Sound card drivers affect your CPU. The higher the WDM slider or ASIO buffers are, the less your CPU will work. The lower your sound card drivers, the higher your CPU will work!!!!!!
 
Thank me!
CJ

May be telling my granny how to suck eggs here..... but if I'm doing anything audio/daw related I turn off my network adapter as well as the various shields that AVG uses as well as any un-needed processes that are running thereby ensuring that if a problem occurs its not network/internet related.
 
I never boter when doing midi/daw related things as midi data is smaller than audio so my head tells me this shouldnt be an issue

What kind of power supply are you using?....And are you using a power surge bar?...Just off the wall, out of mind stuff like that, should be checked, when all the other tips and tricks fail......but power supplies/ electrical surges can cause issue....Take it from some one who has experience....lol.
 
 
 
 

Thanks for the input here, really appreciated.
 
The soft synth I had most issues with (and it can happen even when its the one and only track and soft synth in the project) is U-He's Diva. Using that on some patches causes the furst yellow bar on my CPU performance metre to spike in the red. There is a multicore button in Diva patches, and when turned ON that made things work a lot better (no spikes so far) - (I don't know what that little button does but it works).
 
I do habitually have internet ON, whilst working with Sonar, and recently noticed that does noticably have an adverse affect on performance, so I now disable the connection each time I work with Sonar.
 
So far those 2 things alone have helped a lot, although on some projects the first yellow bar looks like its about to peak into the red on occasions, but so far has not.
 
As for power - I have one plug to the wall into a adapter with 8 earthed sockets, so everything is going into one power source, PC, Midi controller, monitors etc.
 
Re the ASIO buffers, doing some tests I see 64 causes regualr spikes, 1024 has noticable latency, and 256 seems to be the right balance for my system between usability and perfomance.
 
Re Windows, I have Windows 7, set for "Best Performance" but other than that I have done no special tweaks.

IIRC, Diva has a reputation as a CPU hog. In addition to the mutlicore setting there is also an accuracy settingnear the bottom center of the UI with four levels: draft, fast, great and divine. Try lower this setting.

To confirm scook - yes, Diva is known to require a lot of CPU power.

diva has "quality" settings if your machine can't handle the "ultra-realistic" owic