Which take more CPU usage Asus STX II vs Sound Blaster X7 DAC/Amp?
 
Thx in advance

This is an odd question. Why do you ask? Sound cards don't exactly take CPU usage. They may be able to offload some audio processing functions from the CPU, but this will be pretty negligible, audio processing is not that CPU intensive to begin with.

What you use to play your audio (DirectSound, WASAPI, ASIO, etc) is what's really going to make the difference CPU wise, unless you have a computer with a bus speed under three digits long.

fidai said:

  Which take more CPU usage Asus STX II vs Sound Blaster X7 DAC/Amp?
 
Thx in advance

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I would assume the more audio processes you can pass on to the main CPU, the less work load the audio processor has to do, so you can there for use a smaller audio processor, making the sound card cheaper to manufacture.
Is the question because of a future audio hardware you plan to purchase or is just a question out of curiosity? 

I want to know which of these cards has less impact on cpu, mainly playing Pc games.I use my pc in sli mode and have kinda old cpu i74820 over clocked to 4.3.

It's not 1991 anymore. We don't have to deal with IRQ's anymore; your sound card choice isn't going to affect your gaming performance.
 
You realize audio playback hasn't been a challenge for CPU's since they hit double digits on megahertz (much less gigahertz), and your "pretty old" CPU is an i7 which I don't have to look up to tell you is probably dozen times more powerful than my most powerful computer

vapman said:

  It's not 1991 anymore. We don't have to deal with IRQ's anymore; your sound card choice isn't going to affect your gaming performance.
 
You realize audio playback hasn't been a challenge for CPU's since they hit double digits on megahertz (much less gigahertz), and your "pretty old" CPU is an i7 which I don't have to look up to tell you is probably dozen times more powerful than my most powerful computer

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Ya but some forums talking about USB DAC eats more CPU and slower cuz signal going throw USB and not PCIe while playing FPS games, wanted to know which true since i have both cards. 

fidai said:

I want to know which of these cards has less impact on CPU, mainly playing PC games.I use my PC in SLI mode and have kinda old CPU i74820 over clocked to 4.3.

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The impact on the CPU for audio processing has not seemed to an issue for several years.
As your running multi able graphics cards inside a computer case, you might consider getting an external DAC/AMP.
An external DAC/amp would not have to deal with any electrical noise issues inside the computer case.
Get a lower costing sound card, Asus Xonar DG or DGX or Creative Labs Sound Blaster Z (OEM is fine)
and connect an external DAC, with an optical input, to the sound card.
This way the sound card can still do it's headphone surround sound processing, but the signal, still in a digital form, is sent outside the computer case, so the external DAC/amp.
As long as the audio signal is digital, it's not effected by electrical noise, so having the DAC external, will allow the (external) DAC to convert the digital audio signal, to an analog audio signal.
It's once the signal is converted to analog, is were the noise can creep into the audio signal.

fidai said:

  Ya but some forums talking about USB DAC eats more CPU and slower cuz signal going throw USB and not PCIe while playing FPS games, wanted to know which true since i have both cards. 

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I didn't realize you were asking about a USB vs PCIe device.
 
For what it's worth, time critical audio these days in computer for lowest latency goes onboard first and then PCI/PCIe second.
 
You won't notice any problems at all using a USB DAC but there is greater room for error with a USB DAC than onboard or PCI/PCIe.
 
Onboard will always be most reliable and lowest latency. If your motherboard has digital out consider using that to a DAC.

Since you are using SLI, maybe there's a chance that you have limited PCI-e bandwidth. Installing another PCI-e device might limit the bandwidth to your graphics cards. Like if you only have 16x PCI-e lanes from the processor, your graphics cards might use 8x each, and installing another PCI-e card would result it to 8x, 4x, 4x, so one graphics card gets half the bandwidth. This may not be the case, and if it is it might not affect performance anyway.
 
Adding a card below your graphics cards could affect their air flow for cooling, causing more thermal throttling.

Thank you all very much for the help, tomorrow am gonna get an optical cable and connect from motherboard to X7 DAC and test.

fidai said:

  Ya but some forums talking about USB DAC eats more CPU and slower cuz signal going throw USB and not PCIe while playing FPS games, wanted to know which true since i have both cards. 

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So if you go with a low cost internal sound card and an external (optical) DAC/amp, you will not have the CPU/USB issue.

What MindsMirror said.  Make sure that you have available PCI lanes before you install a PCI audio card.  If your goal is to maximize frame rates, you'll probably get better performance from a USB DAC, assuming that your SLI'd video cards are using all of the available PCI lanes.  If, however, your video cards don't use all of the lanes and you can add a PCI audio card, then that is probably the way to go.

My gut feeling, though, is that going the USB route either way won't cause a noticeable difference in performance.  If it's raw numbers that matter, then, yeah, USB will slow things down, but in real-world performance, you won't notice.