Intel HD Audio Arrives

By Dave Salvator  |  Posted 2004-06-24

Intel HD Audio Arrives

Motherboard audio has long been the ugly stepchild to its PCI-based sibling.

For the longest time, if you wanted really solid audio in your PC, you had to get a PCI-based sound card. That started to change with the arrival of Nvidias nForce chipset, which put three DSPs into the south bridge and encoded Dolby Digital in real time. Nvidias solution seems to have become an orphan for the time being, though the company maintains that its working on further audio solutions. Analog Devices has also championed better motherboard audio through its SoundMAX offerings and companies like SigmaTel have been instrumental in improving the lot of motherboard-down audio. But all have had to deal with the limitations of the aging AC97 standard, which Intel defined about eight years ago. The audio world has undergone some major changes since then and its become increasingly clear that AC97 needs to be retired.

With the arrival of its Grantsdale and Alderwood motherboards using the 925 and 915 chipsets, respectively, Intel has simultaneously brought out three major platform changes: new and improved chipsets, PCI Express, and HD Audio. Youve gotten your first taste of the platforms overall performance, so today well show you Intels new motherboard audio sub-system, where we kick the tires and take it for a test drive.

Next page: Intels HD Audio

Intels HD Audio


The HD Audio initiative, formerly code-named Azalia, had several goals to improve the lot of motherboard-down audio solutions:

  • Intels HD Audio specification defines the controller, link, and board implementation of motherboard-down audio hardware.

  • Seeks to create a single audio driver that can be used with all compliant hardware.

  • Supports up to 15 simultaneous audio streams, supporting resolutions up to and including 192KHz/24-bit to enable two-channel playback for DVD-Audio and enough bandwidth for 96KHz/24-bit multichannel DVD-A. No DVD-Audio player application with full support of encrypted DVD-A is yet available, however. HD Audio also allows multiple codecs on a single motherboard to operate autonomously. One codec would drive the rear speaker outputs, a second could accommodate line-level input coming in from front-panel jacks, as well as microphone and headphone jacks. These two audio sections can operate independently of one another.

  • Allow multiple codecs on a single motherboard to operate autonomously. One codec would drive the rear speaker outputs, a second could accommodate line-level input coming in from front-panel jacks, as well as microphone and headphone jacks. These two audio sections can operate independently of one another.

As you can see from this diagram, HD Audio will be able to drive multiple codecs that can operate independently of one another, allowing different numbers of streams to be routed through each codec at different sampling rates. The architecture also specifies a "multi-client" implementation wherein a single programs audio chores can be tasked to a specific DMA engine. So rather than have a single app take complete ownership of the audio hardware, multiple applications can have audio being processed simultaneously.

Next page: How we tested

How we tested


To start off, we put the Intel HD audio sub-system through our usual audio obstacle course:

Test Purpose
Audio WinBench 99 1.1 Measures CPU usage playing sounds via DirectSound and DirectSound3D. We measured CPU usage while playing 32 simultaneous sounds, using both static and streaming buffers
RightMark Audio Analyzer 5.3 Measures audio signal quality and measurements including frequency response, noise, dynamic range, intermodulation distortion, THD+N, and stereo crosstalk
Close Listening Tests
(using headphones)
Measures circuit noise, hash, and blitter noise. We used a set of Shure e5c in-ear earphones to assess the headphone jack and the front right/left output
3DMark Sound Test Runs the benchmarks Game Test 1 scene at 640x480, first with no sound, then with 24 sounds, and finally with 60 sounds if the hardware supports it
Ad Hoc Game Tests We ran Unreal Tournament 2003 and Call of Duty benchmarks (with various audio settings enabled) to see performance impact on real games

Our test system had the following components:

  • Intel 3.4GHz Pentium 4 Extreme Edition
  • Intel 915GUX motherboard with the Intel 915G chipset
  • 1GB of DDR-2 SDRAM
  • Nvidia GeForce 6800 Ultra PCI Express 3D card (NV45) running 61.45 drivers
  • Two TK S-ATA hard-drives running in a RAID 0 configuration
  • DVD/CD-R/W combo drive
  • Windows XP with SP1
  • DirectX 9.0b

We first tried to bring up HD Audio on a 925X motherboard made by Intel, but the audio section was apparently DOA. Unfortunately the audio output on the 915GUX board is stereo-only, so we didnt get a chance to conduct multi-channel audio listening tests. We were able to successfully run multichannel audio on a different 925X system, but werent able to run extensive tests on that system.

Next page: Test results

Test results

Generally speaking, the Realtek HD Audio solution delivered good but not great signal quality performance and received no boost from running at 96KHz/24-bit. For our signal quality testing, we turned off Intel Audio Studios DSP algorithms, since they change the spectral characteristics of the audio output.

RightMark Audio Analyzer Tests

96KHz/24-bit 44KHz/16-bit
Noise level, dB (A): -85.7 -85.5
Dynamic range, dB (A): 80.7 81.8
THD, 0.0065 0.0067
IMD, 0.018 0.019
Stereo crosstalk, dB: -82.4 -85.3

As you can see, Realteks 44KHz/16-bit numbers arent bad, though theyre not the best motherboard-down audio numbers weve seen either. Theyre also nowhere close to approaching theoretical on dynamic range, which would be around -96dB. THD and IMD numbers are quite good, however--on par with decent home stereo gear.

Going to 96KHz/24-bit, we got no improvement in performance, which was disappointing. We would have been pleasantly surprised to see the Realtek part break the -100dB barrier, but we were hoping to see it get into at least the mid-90s, but it wasnt to be. Distortion was still nice and low, but its pretty apparent that whatever noise floor is present affects both resolutions equally and also masks whatever improvement 96KHz/24-bit was going to net.

Next page: Audio WinBench

Audio WinBench

The news here isnt good at all. CPU usage starts out high and goes even higher when we turn on Intel Audio Studios (IAS) DSP effects. On its own, Realteks Sensaura implementation is already riding high at around 13% for DirectSound and close to 20% on DirectSound3D. But adding IAS to the mix pushes those numbers up 10 percentage points on both APIs, with DirectSound at around 23% and DirectSound3D at close to 30%. When you consider that were running on a very beefy 3.4GHz Pentium 4 Extreme Edition CPU, these numbers are that much more disappointing.

3DMark Sound Test

The news here gets considerably better. Running both with IAS enabled and disabled, you can that in both cases turning sound on costs very little in terms of lost frame-rate. With IAS turned off, we see a 2.5% dip (1.6fps) in frame rate, and with IAS turned on, the frame rate drops 4.4% (2.6fps). Both figures are essentially in the noise (so to speak) and indicate that despite the disappointing Audio WinBench numbers, game frame rates shouldnt suffer because of the Realtek HD Audio solution.

IAS overhead however is a bit more noticeable. Even with no sounds running, we saw a 10.4% (6.9fps) drop in frame rate. And with eight sounds there was a 12.2% (7.9fps) drop compared to running with IAS disabled. These frame rates arent terrible, and in a game running in the 60+fps range, would barely be noticed. Where it could make a difference is in a situation where frame rate is already marginal, say around 25-30fps, and the overhead of IAS pulls it down a bit further into noticeable stuttering.

Ad-Hoc Game Tests

We ran the Call of Duty benchmark built into the 1.2 patch of the game, plus the Unreal Tournament 2004 benchmark. UT2004 saw only a minor frame rate hit when turning on hardware 3D audio with EAX. The frame rate dropped from about 67fps with default audio settings to about 65fps with EAX support.

Call of Duty was another matter, however. When using the Miles fast 2D positional audio, we witnessed frame rates of 173 fps. On the other hand, when we turned on EAX1 or EAX2 support, the frame rate dropped to the low 60s. We werent able to run EAX3 -- the game would return to default audio if we tried to run with EAX3 enabled.

Next page: Hands-on time/subjective observations


-on time/subjective observations ">

The first thing we noticed was that for all the bells and whistles found in Intel Audio Studio (IAS) and in Realteks own audio control panel, neither application has a mixer in it to replace Microsofts clunky old standard mixer applet. Also known as the kernel mixer (Kmixer), this applet is very long in the tooth and its UI has needed a serious face lift for many moons. Granted, the mixer is a Microsoft application since its part of the OS, but any Windows audio hardware worth its salt gives you a better mixer than the one Windows provides by default.

Microsoft actually brought forth a new audio architecture in the OS to make way for Intels HD Audio had a hand in developing HD Audios OS interfaces. This new architecture, called Universal Audio Architecture (UAA), is intended to enable HD Audio and provide more robust audio interfaces for FireWire- and USB-based audio devices. According to Microsoft, UAAs goals are:

  • Simpler installation of audio peripherals
  • Higher performance: Minimum CPU time consumed when streaming, while taking advantage of increased bandwidth
  • Glitch-free audio
  • Ability to update the operating system while guaranteeing high-quality audio performance
  • More stable and secure audio for server applications
  • Fewer drivers and upgrades required and less driver code to be developed, tested and supported
  • Reduction in support calls and returns

While these are all laudable goals, we still wish a new and improved mixer application had made its way into the feature list as well.

You Dont Know Jack

One of HD Audios most visible features is its jack-sensing technology, which ensures you make the proper connections to the growing number of output and input jacks that now populate back panels of motherboard-down audio solutions. Realteks implementation fares pretty well, where the driver senses a jack insertion event by "listening" for impedance changes in the jack.

Each time we plugged in a line-input or line-output, wed be prompted by the Realtek control panel app to verify that what we plugged in was in the correct jack. After about the fifth prompt, this implementation, though well-intentioned, started to get annoying. Weve seen smarter implementations from Analog Devices and SigmaTel that not only sense a change in impedance in the jack, but also can distinguish the amount of change in impedance and figure out whether a line-input or a microphone was just plugged in. They can also distinguish between a line-output and a pair of headphones. So even if you plug an input or output into the wrong jack, the driver can re-patch channels to ensure the wiring configuration, even if erroneous, will still work.

Next page: Intel Audio Studio

Intel Audio Studio


Intel partnered with Sonic Focus to create Intel Audio Studio, a new bundled audio application that arrives with Intel motherboards. For the D925XCV, D925XBC, and D915PBL models, IAS is free and included on the installation CD. On other models like the D915PGN, D915PSY, D915PCY, D915PCM, D915GAG, D915GAV, D915GEV, and D915GUX, a 20-use no-obligation trial version can be downloaded and purchased for $14.95. Intel is also working on a version of IAS that will work on some 865-based motherboards that can also be downloaded and then purchased for $14.95.

Sonic Focus technology touts the following features:

  • MP3 audio quality restoration improves high sample-rate MP3 files close to CD quality, while dramatically improving lower-rate MP3 files.

  • Full-range clarity enhancement adds vocal warmth and clarity to movie and game dialog and brilliance to solo instruments.

  • Dynamic range compensation energizes the audio stream, enabling users to turn up the volume without a perceived fall-off in bass response.

  • Audio environment modeling puts users in control of sound stage; studio acoustics are preconfigured by professional audio engineers to complement different media types and configurations of speakers and headphones.

  • Bass definition processing analyzes and intelligently manages low-range signals, without muffling the midrange.

  • Adaptive waveform analysis analyzes and adjusts audio streams based on content, with no requirement for users to constantly adjust settings.

  • Distortion filtering through special DSP filters preserves sound quality while minimizing distortion.

We spent some time playing with IAS knobs and levers and unlike most software audio "enhancement" applications, we actually liked this one. Weve been subjected to countless apps that claim to enrich the audio experience and within five minutes of being "enriched," we find ourselves reaching either for the off-switch or a ball-peen hammer. However IAS does a good job of subtly applying its DSP effects to music material to good effect. Sonic Focus is doing some pretty serious DSP leg-work to achieve its effect that goes way beyond simple EQ tweaks, though some of the effects sound like good EQ adjustments. IAS is especially useful in tweaking audio being played through marginal speakers, where certain types of frequency response are lacking.

Next page: Final thoughts/what to buy

Final thoughts

/what to buy ">

Were glad to see a major revision made to Intels motherboard-down audio architecture. AC97 had clearly run out of gas and HD Audio marks both an improvement now, and its flexibility will enable some interesting implementations up the road. That said, there are still some pieces missing from the puzzle. For starters, there is currently no DVD-Audio player that can be used with Intels HD Audio to enable that content format. Given HD Audios design specifications—multichannel 96KHz/24-bit and two-channel 192KHz/24-bit—it was clearly aimed at being able to enable playback of DVD-Audio content, but the software support isnt yet in place. Hopefully, InterVideo and CyberLink will step up and enable DVD-Audio on Intels HD Audio platform in their respective applications: WinDVD and PowerDVD.

Also missing is support for SACD, although here the limitation is the lack of available drives that have the necessary 1-bit D/A converters. Intel has stated that it may add support for SACD later this year, but until drives come to market that truly enable this format, it will be something of a moot point.

The Intel Audio Studio application is a nice extra that will adorn several of Intels latest motherboards and will be offered as an up-sell on many more. Its a nice addition, though on those systems where it doesnt arrive gratis in the box, its not an absolutely critical application that youll need to buy.

Wed still like to see an improved mixer application become standard equipment in Windows. The Kmixers UI has remained unchanged since Windows 95, and its high time to bring that app into the 21st century.

Game performance is a mixed bag. Using the default audio in games seems to generate only a minor frame rate hit. But sophisticated 3D audio is increasingly becoming important in many games. A game like Thief: Deadly Shadows is a completely different animal if you can play it with full positional sound support. Perhaps better performance will become possible with better tuned drivers.

Todays chapter doesnt mark the definitive word on Intel HD Audio. In fact, its only the beginning. Well be seeing solutions coming from Analog Devices, SigmaTel, C-Media and Via in the coming months. We look forward to seeing what these companies add to the mix to distinguish their offerings, and the lot of motherboard-down audio should improve markedly this year and next. When we can gather an interesting number of them together, well pit them against each other to see who is the last man standing.

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