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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  • SiliconDoc - Wednesday, September 30, 2009 - link

    No, it's the fact you tell LIES, and always in ati's favor, and you got caught, over and over again.
    That is WHAT HAS HAPPENED.
    Now you catch hold of your senses for a moment, and supposedly all the crap you spewed is "ok".
  • SiliconDoc - Friday, September 25, 2009 - link

    Once again, all that matters to YOU, is YOUR games for PC, and ONLY top sellers, and only YOUR OPINION on PhysX.
    However, after you claimed only 2 games, you went on to bloviate about Havok.
    Now you've avoided entirely that issue. Am I to assume, as you have apparently WISHED and thrown about, that HAVOK does not function on NVidia cards? NO QUITE THE CONTRARY !
    --
    What is REAL, is that NVidia runs Havok AND PhysX just fine, and not only that but ATI DOES NOT.
    Now, instead of supporting BOTH, you have singled out your object of HATRED, and spewed your infantile rants, your put downs, your empty comparisons (mere statements), then DEMAND that I show PhysX is worthwhile, with "golden sellers". LOL
    It has been 1.5 years or so since Aegia acquisition, and of course, game developers turning anything out in just 6 short months are considered miracle workers.
    The real problem oif course for you is ATI does not support PhysX, and when a rouge coder made it happen, NVidia supported him, while ATI came in and crushed the poor fella.
    So much for "competition", once again.
    Now, I'd demand you show where HAVOK is worthwhile, EXCEPT I'm not the type of person that slams and reams and screams against " a percieved enemy company" just because "my favorite" isn't capable, and in that sense, my favorite IS CAPABLE.
    Now, PhysX is awesome, it's great, it's the best there is, and that may or may not change, but as for now, NO OTHER demonstrations (you tube and otherwise) can match it.
    That's just a sad fact for you, and with so many maintaining your biased and arrogant demand for anything else, we may have another case of VHS instead of BETA, which of course, you would heartily celebrate, no matter how long it takes to get there.
    LOL
    Yes, it is funny. It's just hilarious. A few months ago before Mirror's Edge and Anand falling in love with PhysX in it, admittedly, in the article he posted, we had the big screamers whining ZERO.
    Well, now a few months later you are whining TWO.
    Get ready to whine higher. Yes, you have read about the uptick in support ? LOL
    You people are really something.
    Oh, I know, CUDA is a big fat zero according to you, too.
    (please pass along your thoughts to higher education universities here in the USA, and the federal government national lab research facilites. Thanks)
  • SiliconDoc - Thursday, September 24, 2009 - link

    Yes, another excuse monger. So you basically admit the text is biased, and claim all readers should see the charts and go by those. LOL
    So when the text is biased, as you admit, how is it that the rest, the very core of the review is not ? You won't explain that either.
    Furthermore, the assumption that competition leads to something better in technology for videocards quicker, fails the basic test that in terms of technology, there is a limit to how fast it proceeds forward, since scientific breakthroughs must come, and often don't come, for instance, new energy technologies, still struggling after decades to make a breakthrough, with endless billions spent, and not much to show for it.
    Same here with videocards, there is a LIMIT to the advancement speed, and competition won't be able to exceed that limit.
    Furthermore, I NEVER said prices won't be driven down by competition, and you falsely asserted that notion to me.
    I DID however say, ATI ALSO IS KNOWN FOR OVERPRICING. (or rather unknown by the red fans, huh, even said by omission to have NOT COMMITTED that "huge sin", that you all blame only Nvidia for doing.)
    So you're just WRONG once again.
    Begging the other guy to "not argue" then mischaracterizing a conclusion from just one of my statements, ignoring the points made that prove your buddy wrong period, and getting the body of your idea concerning COMPETITION incorrect due to technological and scientific constraints you fail to include, is no way to "argue" at all.
    I sure wish there was someone who could take on my points, but so far none of you can. Every time you try, more errors in your thinking are easily exposed.
    A MONOPOLY, in let's take for instance, the old OIL BARRONS, was not stagnant, and included major advances in search and extraction, as Standard Oil history clearly testifies to.
    Once again, the "pat" cleche' is good for some things ( for instance competing drug stores, for example ), or other such things that don't involve inaccesible technology that has not been INVENTED yet.
    The fact that your simpleton attitude failed to note such anomolies, is clearly evidence that once again, thinking "is not reuired" for people like you.
    Once again, the rebuttal has failed.
  • kondor999 - Thursday, September 24, 2009 - link

    This is just sad, and I'm no fanboy. I really wanted a 5870, but only with 100% more speed than a GTX285 - not a lousy 33%. Definitely not worth me upgrading, so I guess ATI saved me some money. I'm certain that my 3 GTX280's in Tri-SLI will destroy 2 5870's in CF - although with slightly less compatability (an important advantage for ATI, but not nearly enough).
  • Moricon - Thursday, September 24, 2009 - link

    I have been a regular at Tomshardware for a while now, nad keep coming back to Anandtech time and again to read reviews I have already read on other sites, and this one is by far the best I have read so far, (guru3d, toms, firing squad, and many others)

    The 5870 looks awesome, but from an upgrade point of view, I guess my system will not really benefit from moving on from E7200 @3.8ghz 4gb 1066, HD4870 @850mhz 4400mhz on 1680x1050.

    Such a shame that i dont have a larger monitor at the moment or I would have jumped immediately.

    Looks like the path is q9550 and 5870 and 1920x1200 monitor or larger to make sense, then might as well go i7, i5, where do you stop..

    Well done ATI, well done! But if history follows the Nvidia 3xx chip will be mindblowing compared!
  • djc208 - Thursday, September 24, 2009 - link

    I was most surprised at how far behind the now 2-generation old 3870 is now (at least on these high-end games). Guess my next upgrade (after a SSD) should be a 5850 once the frenzy dies away.
  • JonnyDough - Thursday, September 24, 2009 - link

    They could probably use a 1.5 GB card. :(
  • mapesdhs - Wednesday, September 23, 2009 - link


    Ryan, any chance you could run Viewperf or other pro-app benchmarks
    please? Some professionals use consumer hardware as a cheap way of
    obtaining reasonable performance in apps like Maya, 3DS Max, ProE,
    etc., so it would most interesting to know how the 5870 behaves when
    running such tests, how it compares to Quadro and FireGL cards.
    Pro-series boards normally have better performance for ops such as
    antialiases lines via different drivers and/or different internal
    firmware optimisations. Someday I figure perhaps a consumer card will
    be able to match a pro card purely by accident.

    Ian.

  • AmdInside - Wednesday, September 23, 2009 - link

    Sorry if this has already been asked but does the 5870 support audio over Display Port? I am holding out for a card that does such a thing. I know it does it for HDMI but also want it to do it for Display Port.
  • VooDooAddict - Wednesday, September 23, 2009 - link

    Been waiting for a single gaming class card that can power more then 2 displays for quite some time. (The more then 2 monitors not necessarily for gaming.)

    The fact that this performs a noticeable bit better then my existing 4870 512MB is a bonus.

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