I forgot to mention that I also tested with a powered Belkin hub that supports my external USB 2.0 hard drive fine.  I plugged up the original cable into the Belkin powered hub and removed everything else so it could get max bandwidth and it actually sounded worse.

I downloaded, installed and ran the DPC Latency Checker: http://www.thesycon.de/deu/latency_check.shtml

I am getting spikes as high as 2250?s.  I have disabled everything I can in the Device Manager and nothing seems to help.  Any ideas?

dpc latency checker isn't checking your computer's abilty to talk to the Fireface UC, it's checking your computer's internal efficiency.  Unplug the fireface UC completely and you'll still get 2000us latency, I bet.

Until you fix the core issue with your computer, no audio interface will work.

Also, when I have DPC Checker running and let's say SoundForge configured to use ASIO Fireface UC driver, the latency only occurs when actually playing.  If I stop playing in SoundForge, then the latency drops back to < 50?s.  If I use the ASIO Echo Layla24 driver, it never even goes above 50?s.

What do you mean check the BIOS for clock down states?  My BIOS' clock is working fine.  I am not sure I have the room for another PCI card.

Here are the various BIOS options in my Dell 670:
http://support.ap.dell.com/support/edoc … dvfeat.htm

Looks like Speedstep is OFF (my proc runs at 3.4ghz all the time), but where do I disable C1E or enhanced halt state?

Now my primary concern is why in the world the CPU usage is SO much higher for my Fireface UC vs Layla24 PCI.  Any ideas folks?

Here's some tests I ran...

1) Windows Media Player + FF UC = CPU ~ 50% (this one concerns me the most, b/c it makes the least sense)
2) Windows Media Player + Layla PCI = CPU ~ 5%
3) Cubase 3 + FF UC = CPU ~ 50%
4) Cubase 3 + Layla PCI = CPU ~ 30%

Interesting, my Dell 670 seems to have the Intel ICH5 -> www.intel.com/assets/pdf/datasheet/252516.pdf

So these USB issues are solved with any Intel ICH >7 according to your findings?  I am planning on getting one of the new Mac Pros whenever they announce them (hopefully at WWDC next week).  I just wanna make sure that CPU usage won't be around 50% on one of these. 

I guess I could test it on my unibody MacBook.

So would my USB CPU problems be alleviated by using a PCI USB card? If so, what does RME recommend?  Something like this? http://www.newegg.com/Product/Product.a … -_-Product

Yes. Old USB chipsets are the reason for the bad reputation of USB (besides the previous FireWire marketing from Apple). I got an iMac 27 i5 on my desk and it can run with 32 samples on USB.

I think it will help, when it provides a modern USB chipset.

best regards
Knut

No, but it should be no no-name product and provides a modern chipset (ICH10). Don?t forget, the processing power of your old PC will not allow ultra-low latencies, but the situation will improve.

Yes. Logic audio setup. 32 samples buffers in a small project.

best regards
Knut

NEC is usually quite ok, as far as I know. Not aware of any problems at least...
Cheaper card often come with VIA chips.

Regards
Daniel Fuchs
RME

Belkin and Delock make such cards, and I'm sure there are others...

Regards
Daniel Fuchs
RME

Correction, the hiccups are more like the sound you'd get if you looped something on say 1/16th note interval.  It's weird.  It's not at all related to buffer size/drop outs/noise.

What exactly is the standard audio device you've chosen in the Windows Control Panel?

Regards
Daniel Fuchs
RME

I've had a similar problem, maybe the same one you are having. 

I found that if I had an audio application like Soundforge open (using outputs 1+2 of the FFUC in Soundforges audio setup) and then I tried to open Windows Media player to play another audio file (also using outputs 1+2 set in the XP control panel) while Soundforge was still open, then I would get this problem.  A really terrible crackling sound!!!

I noticed that the problem wouldn't happen when using programs individually.  So it seems that the FFUC (by default) has a problem when 2 or more applications are sharing the same audio outputs of the FFUC.  I never had this problem with other brand name soundcards.  So I knew something strange was going on!!

So what I did... which solved the problem... is in XP control panel, I set the default audio decive to FFUC Outputs 7+8.  This meant that Windows Media Player was now using 7+8 as it's outputs and Soundforge was using outputs 1+2.

It seems that when you set the default audio device in XP contral panel, your not selecting the physical outputs 7+8 (which is the headphones)... your selecting software playback channels 7+8.  Software playback channels are shown in Total Mix in the middle row.  You can then route any combination of Audio Inputs and Software Playback Channels to the any physical output such as your headphones or your speakers.  Total mix is very powerful but if your used to any other soundcards, this isn't an issue but of course you wouldn't have the same mixing control.  I think the problem is getting your head around the concept of Total Mix. 

I found this video was helpful...
http://www.youtube.com/watch?v=SwoKoxYfzds

I hope this helps.

It's gotta be the PCI-e card or it's drivers, b/c I just tried a standard PCI USB 2.0 card from PPA Int'l and it had no issues.  However, the standard PCI card offers no improved CPU performance over going with the motherboard USB.  Ughhh.  I am going to try 1 more PCI-e USB card and report back.

RME, does your latest Fireface UC driver support USB 3.0 chipsets such as the NEC uPD720200?

Gotcha. 

I guess I have to find a USB 2.0 PCI-e interface then.

Am I wrong for thinking that a PCI-e USB card should improve CPU strain and latency vs just going with my motherboard? 

How come with my Echo Audio Layla24 with PCI card I get:
5-20% CPU usage with just a .mp3 file in Windows Media Player
Max 104?s latency from DPC

We found that there is an minor issue with the NEC usb 3 Controller.
At the moment buffersizes > 256 sample (SS),  are not working properly.
So at the moment you should either use the ASIO driver or set the buffersize in the settings dialog to 256 or below if you want to use the WDM driver.
/Uwe