X-Fi Processing Elements: The Quartet DSP

Audio effects and processing can be done on a CPU. The latest audio solutions from Intel employ software from Sonic Focus that performs audio processing without the aid of dedicated hardware. If an end user wishes to enable advanced filtering or processing features, the Creative X-Fi has the advantage of being able to perform these tasks without tasking the CPU (thereby freeing up resources for other applications).

As is often the case, a general purpose CPU is not the most efficient hardware for the job. The Quartet DSP is able to make quick and efficient work of audio data. As mentioned before, the Quartet is made up of 4 independent two-issue SIMD engines, which Creative calls a TIMD architecture for Thread Interleaved and Multiple Data. The configuration of the SIMD paths in Quartet lend themselves well to audio processing.

Creative didn't tell us how wide the data path is down each SIMD pipe, but Quartet is able to handle either integer or floating point data, making it more flexible than DSPs used on older Creative parts. Special instructions allow differing operations to be performed on SIMD data to enable more efficient audio processing. For instance, the FADDSUB2 instruction performs an add-on-one data path and a subtract on another. The DSP is also able to perform complex floating point math with the real and complex results completing in different paths.

In traditional DSP architectures, raw speed often wins out over programmability. Tradeoffs are always necessary, but the Quartet offers a good balance. The result of one instruction can be used in the next with no stalls or reordering necessary and any instruction can be performed after any other instruction without any conflict. Also, any register can be used as any operand in any instruction. While we don't have all the details on the hardware, a high level language compiler could easily target and optimize for this architecture.

At this point, an easy to develop and efficient compiler only really helps Creative write driver and feature code more easily. It could be possible for Creative to allow developers access to their compiler in order to develop specialized DSP code. We don't know if Creative will actually pursue this in the future, but the option is there should they choose to do so.

To sum up the capabilities of the Quartet DSP, we have this list of features:
  • 2 SIMD units per each of 4 simultaneous threads
  • fixed and floating point data supported
  • 235 opcodes
  • up to 1200 MIPS
  • can perform up to 4 moves per instruction
  • easy to compile and optimize
Bringing the entire Audio Ring architecture together, Creative has quite a powerful solution that can handle lots of quick and efficient processing. Multiple audio streams with multiple sample rates can be floating around, being processed and reprocessed with high efficiency and low latency. This gives Creative a good deal of freedom in how heavily they can process audio without needing any assistance from the CPU.

X-Fi Processing Elements: Exploring the SRC New Features, Possibilities, and Modes
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  • JNo - Thursday, September 1, 2005 - link

    In fact, if Anandtech could do a review of the HDA X-Mystique 7.1 it'd be appreciated as I've heard quite a few good things about this card, not least its reasonable price point and dolby digital live output.

    By the way, on a separate note, for all the people here giving anandtech grief, people should look at more than just one site before making informed purchasing decisions and anandtech did much better than tomshardware which was extremely partisan. Also, I would like to use and trust dedicated sound sites like www.3Dsoundsurge.com but unfortunately they are often too slow in reviewing new hardware...
  • DerekWilson - Tuesday, August 30, 2005 - link

    you can output sound digitally ... dolby sources (DVDs) can be output to a reciever, and audio can be output via SPDIF to a reciver as well ...

    What you can't do is take a source that's not already dolby (like music, games and the like), encode it to dolby, and then send it to a reciver.
  • Lwood - Tuesday, August 30, 2005 - link

    I found this on the ALSA mailing list (http://www.gossamer-threads.com/lists/linux/kernel...">http://www.gossamer-threads.com/lists/linux/kernel...:

    "We are not going to get any support from Creative for the X-Fi chip.
    We do not get support from Creative for any Creative chip that has a DSP
    in it."

    It looks like we won't see a Linux driver for the X-Fi anytime soon... :-(
  • sprockkets - Tuesday, August 30, 2005 - link

    Oh well, even nVidia's soundstorm worked in linux, and with the 5.1 encoding out.
  • Reflex - Tuesday, August 30, 2005 - link

    I've had these cards in my lab and all I can say is that this is the first time I've ever really doubted Anandtech's credibility. This reads like a spiced up piece of PR from Creative, and subjective listening would not put this as the best consumer audio solution as so prominently stated on the first page of the review.

    Derek - What the hell is going on here? You don't even include any results from competing products to make such a statement. The war was over before a shot was fired is the impression this review gives. The fact that Creative finally has a card to match the specs that otehr cards have had for three years now makes it a 'revolution'? Sorry, I have been working with these cards for months now and they definatly are nothing special. Just expensive.
  • flexy - Tuesday, August 30, 2005 - link

    100% agree...tried to keep my complaints back, tho.

    Btw. nice nick :)
  • DerekWilson - Tuesday, August 30, 2005 - link

    Hello,

    We will be looking at more cards, and including an envy24 based solution is something that we intend to do in the future.

    We do include a result from a competing solution -- the Gina 3G is a pro audio card which has excellent audio quality. The Elite Pro is closer to a pro audio product in the component selection and construction.

    envy24 based consumer products don't score as well as the Gina 3G from what we have seen. Granted we do have to test this for ourselves, but we would certainly expect the Gina 3G to outperform something from Terratec or M-Audio.

    That being said, the X-Fi outperforms the Gina 3G in just about ever test we ran.

    It is very difficult to subjectively compare audio between cards. There have been some cases (the audigy line) where there was a very clear problem with the aural experience. With the X-Fi line, we can no longer say that we can hear problems with the audio.

    We spent days listening to this card, the Gina, and the Audigy 4. We frankly disagree with the statement that subjective listening does not put this card on par with the best audio solutions out there. We found no reason in our subjective listening tests to conclude otherwise.

    On top of that, after simply listening to the card for days, we ran the RMAA tests. These tests showed clearly that not only was the card void of any issues, but that the quality of the output was much closer to the source than any other card we tested. These two points add up to the conclusion you disagree with.

    And as we said, if this card performs better than the Gina 3G and the Gina performs better than consumer level envy24 parts, it stands to reason that the X-Fi would outperform just about everything but a LynxTWO ... and even then we would need to run some tests of our own ...

    The big problem is that at these incredibly low noise levels, high dynamic range, low distortion, good separation, etc... it is very difficult to hear differences in the audio. To the average person, the audigy 4 Pro, Gina 3G, and X-Fi will sound exactly the same. To a hardcore audiophile, we wouldn't doubt it if the X-Fi won their hearts. The X-Fi (in spite of its features) can provide a very true-to-the-source signal with less coloration than all but the best pro audio cards out there.

    For musicians, the high quality provides a better platform for work than the rest of the pack -- unless, of course, balance audio is desired.

    Show me a consumer audio card that matches the specs of the X-Fi ... From the tests other people have performed on the LynxTwo B at 16-bit/44.1kHz (the unofficial standard in PC audio quality), the X-Fi posts http://audio.rightmark.org/test/lynx-two-b-1644.ht...">better numbers in every category but frequency response (and it's darn close in that area)...

    The high end components used do not make the X-Fi Elite Pro "nothing special" ... They make it nothing most people will need. And certainly, between this and other products that use good quality components, most people won't notice much (if any) difference.

    We very much agree that the card is too expensive. And please rest assured that we will be comparing this card to an evny24 based solution -- and hopefully a lynxtwo -- in the future.

    Thanks for the feedback,
    Derek Wilson
  • yacoub - Wednesday, August 31, 2005 - link

    Look into the BlueGears X-Mystique. It's pretty much the best PC soundcard available at a reasonable price right now - and it's not Creative so there's no assorted bloatware to install.
  • Reflex - Tuesday, August 30, 2005 - link

    Derek -

    I am not trying to bash you here, however you have to understand that when you start an article by proclaiming something the best in its class, but then your test does not include the other solutions in the class at all, that things seem fishy.

    I work with audio devices for a living. I've worked with the X-Fi since it was a prototype(as have a couple dozen other people in my lab). Certainly it is an improvement over previous Creative efforts, and at first we were a bit wowed by the paper specs and proposal. However after working closely with it for months, I honestly can say that no one here feels its anything special. Perhaps some of that is the novelty wearing off, but in any ad-hoc test with someone who hadn't heard it before, they could rarely tell the difference between it and an Audigy, and the M-Audio Revolution generally was said to produce clearer sound. Not that our tests were scientific or anything, we weren't trying to write articles for publication.

    I'd really suggest some blind tests with a variety of content. I think you may be suprised to find that while for MP3's the X-Fi sounds good, for CD's and especially SACD's the mid-range is poorly reproduced. Make certain you use a wide range of music, and prefferably classical numbers that you know very well.

    Something else is you could list what type of speakers/headphones and recievers you are using, if you are testing with something like Klipsch then your credibility would go down considerably for anything but games and action movies, after all the card cannot make up for poor speakers(when measured by reproduction accuracy, not volume).

    I would suggest establishing a baseline and going from there. Based on my experience, in the 'consumer' segment the M-Audio Revolution 7.1 is a good baseline, however any baseline that you could compare against would be beneficial to strengthening the credibility of the review. Granted anything audio is subjective, but when you say something is 'better' you need to at least be able to point to some specific reasons as to why.

    And finally, the section that read like Creative marketing PR was your explanation of their audio architecture. There is nothing inherantly 'better' about the approach Creative is taking, it is simply different, there are both advantages and drawbacks. Furthermore, while they make the product seem like the 'next generation of audio' no one has managed to get a commitment from them to support the upcoming Windows Audio Architecture that will be a part of Vista, without that support they will be behind several others. Their lack of support for Linux is also a drawback for many.

    Thank you for the effort, I hope that this feedback will help you improve your audio reviews in the future. I have read AT since the beginning and rarely doubted what is posted here, there just seemed to be some rather glaring flaws in how this review was handled. At least in my humble opinion.
  • DerekWilson - Wednesday, August 31, 2005 - link

    Thank you very much for the helpful feedback. Some of your suggestions will absolutly make it into future audio reviews.

    I would tend to disagree with your assesment of Creative's architectural direction. If the intent is to very heavily process many audio streams, then the flexibility and power are helpful. This could be a boon to game designers or electronic musicisans looking for some hefty sample rate or dsp power.

    For straight up listening to a single source or recording the architecture is unnecessary.

    I agree that windows driver and linux support are drawbacks as well.

    We absolutely appreciate and need our readers feedback. Thanks for taking the time.

    Derek Wilson

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