DirectCompute, OpenCL, and the Future of CAL

As a journalist, GPGPU stuff is one of the more frustrating things to cover. The concept is great, but the execution makes it difficult to accurately cover, exacerbated by the fact that until now AMD and NVIDIA each had separate APIs. OpenCL and DirectCompute will unify things, but software will be slow to arrive.

As it stands, neither AMD nor NVIDIA have a complete OpenCL implementation that's shipping to end-users for Windows or Linux. NVIDIA has OpenCL working on the 8-series and later on Mac OS X Snow Leopard, and AMD has it working under the same OS for the 4800 series, but for obvious reasons we can’t test a 5870 in a Mac. As such it won’t be until later this year that we see either side get OpenCL up and running under Windows. Both NVIDIA and AMD have development versions that they're letting developers play with, and both have submitted implementations to Khronos, so hopefully we’ll have something soon.

It’s also worth noting that OpenCL is based around DirectX 10 hardware, so even after someone finally ships an implementation we’re likely to see a new version in short order. AMD is already talking about OpenCL 1.1, which would add support for the hardware features that they have from DirectX 11, such as append/consume buffers and atomic operations.

DirectCompute is in comparatively better shape. NVIDIA already supports it on their DX10 hardware, and the beta drivers we’re using for the 5870 support it on the 5000 series. The missing link at this point is AMD’s DX10 hardware; even the beta drivers we’re using don’t support it on the 2000, 3000, or 4000 series. From what we hear the final Catalyst 9.10 drivers will deliver this feature.

Going forward, one specific issue for DirectCompute development will be that there are three levels of DirectCompute, derived from DX10 (4.0), DX10.1 (4.1), and DX11 (5.0) hardware. The higher the version the more advanced the features, with DirectCompute 5.0 in particular being a big jump as it’s the first hardware generation designed with DirectCompute in mind. Among other notable differences, it’s the first version to offer double precision floating point support and atomic operations.

AMD is convinced that developers should and will target DirectCompute 5.0 due to its feature set, but we’re not sold on the idea. To say that there’s a “lot” of DX10 hardware out there is a gross understatement, and all of that hardware is capable of supporting at a minimum DirectCompute 4.0. Certainly DirectCompute 5.0 is the better API to use, but the first developers testing the waters may end up starting with DirectCompute 4.0. Releasing something written in DirectCompute 5.0 right now won’t do developers much good at the moment due to the low quantity of hardware out there that can support it.

With that in mind, there’s not much of a software situation to speak about when it comes to DirectCompute right now. Cyberlink demoed a version of PowerDirector using DirectCompute for rendering effects, but it’s the same story as most DX11 games: later this year. For AMD there isn’t as much of an incentive to push non-game software as fast or as hard as DX11 games, so we’re expecting any non-game software utilizing DirectCompute to be slow to materialize.

Given that DirectCompute is the only common GPGPU API that is currently working on both vendors’ cards, we wanted to try to use it as the basis of a proper GPGPU comparison. We did get something that would accomplish the task, unfortunately it was an NVIDIA tech demo. We have decided to run it anyhow as it’s quite literally the only thing we have right now that uses DirectCompute, but please take an appropriately sized quantity of salt – it’s not really a fair test.

NVIDIA’s ocean demo is a fairly simple proof of concept program that uses DirectCompute to run Fast Fourier transforms directly on the GPU for better performance. The FFTs in turn are used to generate the wave data, forming the wave action seen on screen as part of the ocean. This is a DirectCompute 4.0 program, as it’s intended to run on NVIDIA’s DX10 hardware.

The 5870 has no problem running the program, and in spite of whatever home field advantage that may exist for NVIDIA it easily outperforms the GTX 285. Things get a little more crazy once we start using SLI/Crossfire; the 5870 picks up speed, but the GTX 295 ends up being slower than the GTX 285. As it’s only a tech demo this shouldn’t be dwelt on too much beyond the fact that it’s proof that DirectCompute is indeed working on the 5800 series.

Wrapping things up, one of the last GPGPU projects AMD presented at their press event was a GPU implementation of Bullet Physics, an open source physics simulation library. Although they’ll never admit it, AMD is probably getting tired of being beaten over the head by NVIDIA and PhysX; Bullet Physics is AMD’s proof that they can do physics too. However we don’t expect it to go anywhere given its very low penetration in existing games and the amount of trouble NVIDIA has had in getting developers to use anything besides Havok. Our expectations for GPGPU physics remains the same: the unification will come from a middleware vendor selling a commercial physics package. If it’s not Havok, then it will be someone else.

Finally, while AMD is hitting the ground running for OpenCL and DirectCompute, their older APIs are being left behind as AMD has chosen to focus all future efforts on OpenCL and DirectCompute. Brook+, AMD’s high level language, has been put out to pasture as a Sourceforge project. Compute Abstract Layer (CAL) lives on since it’s what AMD’s OpenCL support is built upon, however it’s not going to see any further public development with the interface frozen at the current 1.4 standard. AMD is discouraging any CAL development in favor of OpenCL, although it’s likely the High Performance Computing (HPC) crowd will continue to use it in conjunction with AMD’s FireStream cards to squeeze every bit of performance out of AMD’s hardware.

The First DirectX 11 Games Eyefinity
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  • mapesdhs - Saturday, September 26, 2009 - link


    > That is quite all right, you fellas make sure to read it all, ...

    But that's the thing S.D., I pretty much don't read any of it. :D (does
    anyone?) First sentence only, then move on.

    Ian.

  • SiliconDoc - Monday, September 28, 2009 - link

    Oh, ha ha, another lowlife smart aleck.

    One has to wonder if you do as you say, and only read the first sentence, and move on, why you would care what I've typed, since you cannot imagine anyone does anything different. Heck you shouldn't even notice this, right liar ?

    Yes, another liar, not amazing, not at all.

    No need to modify or delete the sentence prior to this JaredWalton, smarty pants insulter won't read it, but I'm sure you can't resist, for "convenience's" sake of course.

    Oh, I don't have to bring anything up on topic at all, because neither did lowlife skum not reading, he just got his nose awfully browner.
  • JarredWalton - Friday, September 25, 2009 - link

    Very happy to have everyone here convinced you don't know what you're talking about? That's the only "truth" you've brought to this party. Marketing generally wants reputable people to promote a product - the "every man" approach. Funny that we don't see crazy people espousing products on TV (well, excepting stuff like Sham Wow!)

    Being crazy like you are in this thread only cements your status as someone who doesn't have a firm grip on reality - someone that can't be trusted. Thanks again for clearing that up so thoroughly.

    I am very happy about it as well! :-D
  • erple2 - Tuesday, September 29, 2009 - link

    Yeah, but that "Sham Wow" product works like a freakin' charm...

    http://www.popularmechanics.com/blogs/home_journal...">http://www.popularmechanics.com/blogs/home_journal...
  • SiliconDoc - Wednesday, September 30, 2009 - link

    Im' sure you spend your time drooling in front of a TV after you spank your joystick for fps, so know all about wacky commercials you have memorized, and besides, it's a pathetic, all you have left insult, off topic, who cares, pure hatred, no real response, and the 5870 double epic fail IS THE HOTTEST ATI CARD OF ALL TIME!
  • erple2 - Wednesday, September 30, 2009 - link

    What's with the personal attacks? Does that mean that you concede defeat?

    Meh, you've no more credibility. Chill out.
  • SiliconDoc - Friday, September 25, 2009 - link

    Yeah, now down to insults, since you lost everything else.

    Let's have your claimed specialty outlined here in context, let's have you come clean on LAPTOP GRAPHICS, and spread the truth about how NVIDIA is so far ahead and has been for quite some time, that it's a JOKE to buy a gaming laptop with ATI graphics on board.
    Come on mmister!
    --
    Now that is REALLY FUNNY ! You grabbed your arrogant unscrupulous self and proclaimed your fairness, but picked a spot where ati is completely EPIC FAIL, and NVIDIA is 1000% the only way to go, PERIOD, and left that MAJOR slap in the face high and dry.
    --
    Great job, yeah, you're the "sane one".
    LOL
  • dieselcat18 - Saturday, October 3, 2009 - link

    Nvidia fan-boy, troll, loser....take your gforce cards and go home...we can now all see how terrible ATi is thanks you ...so I really don't understand why people are beating down their doors for the 5800 series, just like people did for the 4800 and 3800 cards. I guess Nvidia fan-boy trolls like you have only one thing left to do and that's complain and cry like the itty-bitty babies that some of you are about the competition that's beating you like a drum.....so you just wait for your 300 series cards to be released (can't wait to see how many of those are available) so you can pay the overpriced premiums that Nvidia will be charging AGAIN !...hahaha...just like all that re-badging BS they pulled with the 9800 and 200 cards...what a joke !.. Oh my, I must say you have me in a mood and the ironic thing is I do like Nvidia as much as ATi, I currently own and use both. I just can't stand fools like you who spout nothing but mindless crap while waving your team flag (my card is better than your's..WhaaWhaaWhaa)...just take yourself along with your worthless opinions and slide back under that slimly rock you came from.
  • JarredWalton - Friday, September 25, 2009 - link

    You've been insulting in this whole thread, so don't go crying to mamma about someone pointing that out. I did go and delete the posts from the person calling you gay and suggesting you should die in various ways, because as bad as you've been you haven't stooped quite that low (yet).

    Laptop issues with ATI... you mean http://www.anandtech.com/mobile/showdoc.aspx?i=356...">like this. Granted, I gave them a chance to address the issues. They failed and my full article on the various Clevo high-end notebooks will make it quite clear how far ahead NVIDIA is in the mobile sector right now.

    "Fair" is treating both sides objectively. ATI has major problems with getting updated graphics drivers out on mobile products, and that's horrible. On the desktop, they don't have such issues for the most part. Yeah, you might have to wait a month or so for a driver update to fix the latest hot release and add CrossFire support... but you have to do the exact same thing for NVIDIA with about the same frequency. Only SLI and CF setups really need the regular driver updates, and in many cases the latest 18x and 19x NVIDIA drivers are slower than 16x and 17x on games that are older than six months.

    Fair is also looking at these results and saying, "gee, I can get a 5870 for $400 (or $360 if you wait a few weeks for supply to bolster up), and that same card has no CrossFire or SLI wonkiness and costs less than the GTX 295 and 4870X2. Okay, 4870X2 and GTX 295 beat it in raw performance in some cases, but I don't think there's a single game where you can say one HD 5870 offers less than acceptable performance at 2560x1600, and I can guarantee there are titles that still have issues with SLI and CrossFire. (Yeah, you need to turn down some details in Crysis to get acceptable performance, but that's true of anything other than the top SLI and CF configs.) I would be more than happy to give up a bit of performance to avoid dealing with the whole multi-GPU ordeal. Why don't you tell us how innovative and awesome tri-SLI and quad-SLI are while you're at it?

    At present, you have contributed more than 20% of the comments to this article, and not a single one has been anything but trolling. Screaming and yelling, insulting others, lying and making stuff up, all in support of a company that is just like any other big company. We don't ban accounts often, but you've more than warranted such action.
  • SiliconDoc - Friday, September 25, 2009 - link

    I think it is more than absolutely clear, that in fact, I said my peace, my first post, and was absolutely attacked. I didn't attack, I got attacked, and in fact you have done plenty of attacking as well.
    I have also provided links, to back up my assertions and counter arguments, added the text for easy viewing, and pointed out in very specific detail whay issues with bias I had and why.
    --
    Now you've claimed "all I've done is post FUD".
    It is nothing short of amazing for you to even posit that, however I can certainly understand anyone pointing out the obvious bias problems (in the article no less) is "on thin ice", and after getting attacked, is solely blamed for "no facts".
    ---
    I certainly won't disagree that the 5870 is a good value as appearing if especially if you don't like to deal with 2 cards or 2 cores.
    But my posts never claimed otherwise. I first claimed it was not as good as wanted, was disappointing, and therefore was not the end of what ati had in store.
    Since I have posted on the 5890, which will in fact be 512 bit.
    Now, you don't like losing your points, or someone adept enough, smart enough, and accurate enough to counter them.
    Sorry about that, and sorry that I won't just lay down, as more heaps are shovelled my way.
    You skip my actual points, and go some other tangent.
    1. PhysX is an advantage and best implementation so far.
    your response: "It sucks because only 2 games ar available"
    ---
    Is that correct for you to do ? Is it not the very best so far ? Yes, it is in fact.
    I have remained factual and reasonable, and glad enough to throw back when I'm attacked.
    But the fact remains, I have made absolutely solid 100% poijnts no matter how many times you claim " lying and making stuff up, "
    ---
    Yet of course, what I just said about NVIDIA and laptp chips, you agreed with. So accoring to your own characterization (quite unfair), all you do is scream and lie, too.
    Just wonderful.
    The GT300 is going to blow this 5870 away - the stats themselves show it, and betting otherwise is a bad joke, and if sense is still about, you know it as well.

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