Are you one of these people who inexplicably gets better performance with Realtek onboard stock sound chipset for soft vst synth output in Sonar, than with an external Edirol UA-25? That shouldn't happen. Something between Sonar and even the latest drivers with my UA-25 still wasn't meshing right. Toggling Computers advanced performance settings from prioritizing Programs to Background services (like ASIO drivers) finally trumped all other optimizations I'd struggled with for YEARS.
Before I get the fantastic guys at Cakewalk or anyone without this issue on the defensive, claiming they have no such incompatibility issues, I freely admit there's no telling exactly what additional variable(s) I perpetually had going on this Windows 7 pc and another Vista one that made it this way for me... buuuut it seems to happen a lot (people well-versed  in settings but with UA-25's getting worse performance in Sonar than their Realtek inferior onboards) so calling me unique would conversely be a stretch. 
 
I'm one of these folks who updated drivers, tinkered with latencies & buffers, eliminated anything else including researching ambiguous processes to shut down... still all 4 cores showed inordinate amount of activity when Sonar 8 Studio (or 6 Home for that matter) ran in Windows 7 or (even Vista it seemed) when using my beloved UA-25, more so than onboard sound! I'd get pops when playing soft synths... just enough to worry about when layers and effects all part of a robust sound program was in some 1 note automated crescendo of panning, chorus, and reverb. Not so much a soft synth running by itself stand-along, but when run as VST plugins in Sonar -- even 1 synth and 1 track if the instrument was an heavy doozie culminating all it's reverberations together like typewriter keys getting stuck.
I have 4 cores AMD-fx-4130 3.8Ghz, Win7Home/64bit/SP1, 8G RAM, Edirol UA-25 newest driver (see post date), set to ASIO... 2 SATA drives, 1 with programs on for recording to...
bad reported latencies and better performance with manual latencie and buffer settings set to annoyingly high -- why?!?!
 
Well, after ever other trick in the book including stuff from an epic post here on it:
 
 
I found one last thing I hadn't tried in years tucked away on Native's pc optimization article:
 
 
and that was:
Windows 7 (and others?): right-click Computer/->Properties->/->Advanced system settings->/
Advanced->/Performance:|settings|/Advanced->
try setting the toggle from prioritizing Programs performance over to BACKGROUND SERVICES!
 
BLAM... all of a sudden for the first time in years all my ram and cores showed a fraction of the mysterious drain/activity, DPC latency tool stopped saying I have "Drivers behaving badly", pops stopped and the number of tracks of "live"-playing MIDI soft synth instruments (not frozen or mixed to audio) I could play without losing integrity skyrocketed!
I swear the sounds even sound fuller if that's possible (they don't lose that hard to describe depth/complexity or start sounding flat or 2D)...
It's a miracle. I switch it back along with other things to do some light gaming, but this is a music game changer I wish I'd tried long ago!
 
 
 

Congrats bro!  I've seen this "optimization" referred to as unnecesary for Windows 7, while other sources still recommend it.  Looks like it could still benefit many systems out there.

I used to do the same thing when I was using a UA-25. I even posted a batch file for toggling foreground/background priority, to which most thread replies were essentially "oh no, that's not necessary". But if it works, it works.
 
When I subsequently upgraded my interface I stopped doing the priority shuffle, as it did not appear to be helpful with the MOTU drivers. Just goes to show that a given optimization might do wonders for one system configuration and not another.

Yes I'm sure many people don't have the same issue despite (almost) all the same environment. I'm not the biggest tech in the world but with peer help it's been my profession:
I'm wondering if motherboard or drivers is a variable?
Whatever the case, without background services chosen I don't always have the issue, but it randomly pops up (so to speak) after playing with different synths even if only 1 at a time, and then choosing the option fixes it every time, except with NI Reactor 5 + Mikro Prism stabilizes the other way (programs) and reduces my first processor's core's use by 10%, so I "freeze synths" (bump to audio and turn them off) where I can and toggle said setting back and forth like you say with a batch shortcut :) :)
 
Cloning hard drive now   with all settings working right...twice, now that every VST plugin and supplemental manual-install weird file extension has been chased down for a week and everything's working after juggling file directories that certain beloved but still flawed (no longer supported) installer programs have gotten wrong without asking the correct one for 5 years... hacking back into old accounts, digging through papers for serials.. I have WAY to many synths and fx but am addicted to each including unfinished projects. I'm going to buy a duplicate motherboard too so the SATA HD clones will boot up & work for me for sure for the next 10 years. There's no such thing as this sound quality becoming obsolete ;P


I have Sonar 8 and would like Session Drummer 3 tho... I can't afford $99 for X just now... 8.5's old hows about a discount on that? Maybe the "essentials" x upgrade has session3?\
I digress :)