rsinger
If your friend isn't familiar with building DAWs and you use an intel chip have them disable C1e in the BIOS.

My bios just says "C states" that can be enabled/disabled/autoed.
 
Disable Speedstep as well (should be nearby C states), that made quite a difference on my system latency-wise.
 
Both are power saving features that are useful, so maybe leave them enabled until you notice a problem.
 

C1e is an enhanced C1 state. C1 is an idle state - if the cpu isn't doing anything it will go idle, which is fine, but when it's enhanced the voltage is also lowered and when the chip wakes up it takes some time for the voltage to rise. If you have an audio driver monitoring an incoming signal or you're recording a signal that may not keep the cpu from going idle and if C1e is enabled you'll get pops, crackles, etc if you try to run quicker than the idle state voltage. I have an i7 3.5 gHz cpu in my DAW and the default setup has C1e enabled, watching the behavior of the chip with ASUS utilities even while I was monitoring an audio signal the cpu would throttle down to 1.4 gHz or something. This was with the microsoft power management stuff set with the min and max values to something like 80% & 100%.
 
I disabled the C1e state and kept the MS power managment stuff set - that way it can throttle back to cool off, but not nearly as much as it was. Just setting the microsoft PM range without disabling C1e did not work on my ASUS mobo.
 
The microsoft performance tools don't give you an accurate reading of the cpu, if you don't have utilities from your mobo manufacturer you need something like the intel power gadget. Start Sonar, enable an audio track so you're monitoring it and then watch the cpu and see how far it throttles back.
 

Paul P
 
My bios just says "C states" that can be enabled/disabled/autoed.
 
Disable Speedstep as well (should be nearby C states), that made quite a difference on my system latency-wise.
 
Both are power saving features that are useful, so maybe leave them enabled until you notice a problem.
 

I'm pretty sure I just disabled C1e in the BIOS and kept speedstep enabled - I think with the AUS mobo I have when speedstep is enable you can control the range (min max) with the microsoft power management feature. I'm a little overclocked, it will turbo up to 4.2, so I want it to be able to throttle back a little since I built it in a quiet case with just one case fan.

rsinger
I'm pretty sure I just disabled C1e in the BIOS and kept speedstep enabled - I think with the AUS mobo I have when speedstep is enable you can control the range (min max) with the microsoft power management feature.

 
That sounds useful and I'll give it a try.  I can't say I like the idea of running my CPU full blast all the time, when I'm idling more often than not.  Going in and out of the bios is a bit of a pain.
 

My PC has been at 100% for about 3 years now, and if it dies I will get a faster CPU and do the same with that one too.
 
I do have it liquid cooled, but it will still likely die prematurely, due to running at full blast.
 
I try to balance it all out by driving only about 7,000 miles a year, and raking the leaves , rather than burning.
 
Bob Bone
 

I am pretty much on board with BBone except I see no reason to use an SSD, and since  7200 rpm hard drives are fast enough for audio, there is no need for SATA 3. You are unlikely to find a contemporary board that does not have SATA 3 in any case, but you will not see any improvement with that connection unless you are running a fast SSD. USB 3 is handy if you are running an external drive (eSATA is functionally equivalent) for anything but backup, but you are better off putting the drive inside the case anyway unless you are using it for backup. The money you save by not using an SSD will give you enough to buy three good sized hard drives, which may possibly give you a meaningful performance advantage that you will not see from an SSD. 

If your friend actually knows what they are doing and is up to date with the latest configurations.
 
The few things they need to get right is the 7200 RPM hard drive  NOT  green either.  
go for quiet components when possible. 
Careful with Video cards with fans, Some processor fans are small and loud,, Big slow moving fans are the ticket or better yet water cooling. 
 
The rest they can make their own decisions based on your budget. 
Sonar will run just fine on anything new that is built right. 
Shop in the middle ground. 
And once it's going run the DPCLAT test and optimize it for audio. Not a big deal most of the time. 
 
 

I only suggest an SSD for a primary drive, since many folks place only the OS and applications on that drive, so the cost of a 240 GB SSD is about the same as a 2 TB regular drive, and if that's all that will live on the drive the SSD drive is still plenty big enough.
 
It's really not a big deal, either way - stay clear of green and split things across at least 2 drives and all should be well.
 
Bob Bone
 

unless you know for sure your friend is a whiz.. go to ebay and get a higher end factory reconditioned PC .. the two computers in my studio were ~$700 each, but would have cost me closer to $900ea to build.