Windows Vista might have done away with much of the hardware assistance that once made discrete soundcards the only choice for gamers, but there’s still the matter of sound quality. Every motherboard in today’s test features "High Definition" audio, and we’re going to find out just what this really means in the land of onboard codecs.

Setting the quality standard is an Asus Xonar D2X sound card, with its superior 118db rated signal-to-noise ratio on analogue outputs. A top quality 118db rated input signal-to-noise ratio also caused us to choose the Xonar D2X as the input device for capturing the audio streams from onboard solutions - except for the Asus P5E3 Premium.

What made the P5E3 Premium different? Its full-volume output levels were not high enough to run our chosen test software through the Asus Xonar D2X line input. The P5E3 Premium’s line-input was slightly more sensitive than that of the discrete soundcard, so we had to use direct "loop-back" mode rather than looping the motherboard output to the soundcard input.

The change could put the P5E3 Premium at a slight disadvantage compared to other boards, because its line-input connection is rated at only 92db signal-to-noise ratio, and the codec’s output-to-input loop is rated at 96db. Yet Asus has only itself to blame for the slightly-handicapped test method used with its P5E3 Premium, since the firm produces both the motherboard and the Xonar D2X sound card.

The Asus Xonar soundcard shows an exemplary frequency response curve, easily extending past the 20 kHz considered the threshold of normal ears. None of the onboard solutions perform poorly, however, as the majority of listeners would find it extremely difficult to discern the difference - consider that the majority of speakers can’t play sounds above 18 kilohertz at reasonable volume levels, and the majority of audio recordings have similar limitations. Gigabyte leads the onboard solutions slightly.

Asus Xonar noise levels are amazingly low, hovering at around -130 dB. While the onboard solutions pale in comparison, and some look very erratic, they all stay below -110 dB throughout most of the tested frequencies. Gigabyte again leads slightly among onboard solutions, and the P5E3 Premium’s moderate loss is probably due in part to its unusual test requirement. All audio solutions surpassed rated signal-to-noise ratios in this test.

All of the onboard audio solutions had good dynamic range, while the Xonar D2X soundcard appears simply superb. Gigabyte retains its lead among onboard solutions.

Any form of noise or distortion that appears only below -110 dB shouldn’t concern most listeners. The Xonar D2X again appears superb, while the GA-X48T-DQ6 onboard solution does slightly better than the "acceptable" results of everyone else.

The stereo crosstalk evaluation showed minimal bleeding between channels, with the Asus P5E3 Premium leading among onboard audio solutions. Asus’ lead might not be all that apparent at first glance, but the other onboard solutions bleed at higher frequencies that are more directional, making the diminished channel separation more noticeable. Yet even the worst-performing MSI X48 Platinum did okay.