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

    I was here before this site was even on the map let alone on your radar, and have NEVER had any other acct name.
    I will wait for your APOLOGY.
  • ol1bit - Friday, September 25, 2009 - link

    Goodbye 8800gt SLI... nothing has given me the bang for the buck upgrade that this card does!

    I paid $490 for my SLI 8800Gt's in 11/07

    $379 Sweetness!
  • Brazos - Thursday, September 24, 2009 - link

    I always get nostalgic for Tech TV when a new gen of video cards come out. Watching Leo, Patrick, et al. discuss the latest greatest was like watching kids on Christmas morning. And of course there was Morgan.
  • totenkopf - Thursday, September 24, 2009 - link

    SiliconDoc, this is pathetic. Why are you so upset? No one cares about arguing the semantics of hard or paper launches. Besides, where the F is Nvidias Gt300 thingy? You post here more than amd fanboys, yet you hate amd... just hibernate until the gt300 lauunches and then you can come back and spew hatred again.

    Seriously... the fact that you cant even formulate a cogent argument based on anything performance related tells me that you have already ceded the performance crown to amd. Instead, you've latched onto this red herring, the paper launch crap. stop it. just stop it. You're like a crying child. Please just be thankful that amd is noww allowing you to obtain more of your nvidia panacea for even less money!

    Hooray competition! EVERYONE WINS! ...Except silicon doc. He would rather pay $650 for a 280 than see ati sell one card. Ati is the best thing that ever happened to nvidia (and vice versa) Grow the F up and dont talk about bias unless you have none yourself. Hope you dont electrocute yourself tonight while making love to you nvidia card.
  • SiliconDoc - Thursday, September 24, 2009 - link

    " Hooray competition! EVERYONE WINS! ...Except silicon doc. He would rather pay $650 for a 280 than see ati sell one card."
    And thus you have revealed your deep seated hatred of nvidia, in the common parlance seen.
    Frankly my friend, I still have archived web pages with $500 HD2900XT cards from not that long back, that would easily be $700 now with the inflation we've seen.
    So really, wnat is your red raving rooster point other than you totally excuse ATI tnat does exactly the same thing, and make your raging hate nvidia whine, as if "they are standalone guilty".
    You're ANOTHER ONE, that repeats the same old red fan cleche's, and WON'T OWN UP TO ATI'S EXACT SAME BEHAVIOR ! Will you ? I WANT TO SEE IT IN TEXT !
    In other words, your whole complaint is INVALID, because you apply it exclusively, in a BIASED fashion.
    Now tell me about the hundres of dollars overpriced ati cards, won't you ? No, you won't. See that is the problem.
  • silverblue - Friday, September 25, 2009 - link

    If you think companies are going to survive without copying what other companies do, you're sadly mistaken.

    Yes, nVidia has made advances, but so has ATI. When nVidia brought out the GF4 Ti series, it supported Pixel Shader 1.3 whereas ATI's R200-powered 8500 came out earlier with the more advanced Pixel Shader 1.4. ATI were the first of the two companies to introduce a 256-bit memory bus on their graphics cards (following Matrox). nVidia developed Quincunx, which I still hold in high regard. nVidia were the first to bring out Shader Model 3. I still don't know of any commercially available nVidia cards with GDDR5.

    We could go on comparing the two but it's essential that you realise that both companies have developed technologies that have been adopted by the other. However, we wouldn't be so far down this path without an element of copying.

    The 2900XT may be overpriced because it has GDDR4. I'm not interested in it and most people won't be.

    "In other words, your whole complaint is INVALID, because you apply it exclusively, in a BIASED fashion. " Funny, I thought we were seeing that an nauseum from you?

    Why did I buy my 4830? Because it was cheaper than the 9800GT and performed at about the same level. Not because I'm a "red rooster".

    ATI may have priced the 5870 a little high, but in terms of its pure performance, it doesn't come too far off the 295 - a card we know to have two GPUs and costs more. In the end, perhaps AMD crippled it with the 256-bit interface, but until they implement one you'll be convinced that it's a limitation. Maybe, maybe not. GT300 may just prove AMD wrong.
  • SiliconDoc - Wednesday, September 30, 2009 - link

    You have absolutely zero proof that we wouldn't be further down this path without the "competition".
    Without a second company or third of fourth or tenth, the monopoly implements DIVISIONS that complete internally, and without other companies, all the intellectual creativity winds up with the same name on their paycheck.
    You cannot prove what you say has merit, even if you show me a stagnant monopoly, and good luck doing that.
    As ATI stagnated for YEARS, Nvidia moved AHEAD. Nvidia is still ahead.
    In fact, it appears they have always been ahead, much like INTEL.
    You can compare all you want but "it seems ati is the only one interested in new technology..." won't be something you'll be blabbing out again soon.
    Now you try to pass a lesson, and JARED the censor deletes responses, because you two tools think you have a point this time, but only with your deleting and lying assumptions.
    NEXT TIME DON'T WAIL ATI IS THE ONLY ONE THAT SEEMS INTERESTED IN IMPLEMENTING NEW TECHGNOLOGY.
    DON'T SAY IT THEN BACKTRACK 10,000 % WHILE TRYING TO "TEACH ME A LESSON".
    You're the one whose big far red piehole spewed out the lie to begin with.

  • Finally - Friday, September 25, 2009 - link

    The term "Nvidiot" somehow sprung to my mind. How come?
  • silverblue - Thursday, September 24, 2009 - link

    Youre spot on about his bias. Every single post consists of trash-talking pretty much every ATI card and bigging up the comparative nVidia offering. I think the only product he's not complained about is the 4770, though oddly enough that suffered horrific shortage issues due to (surprise) TSMC.

    Even if there were 58x0 cards everywhere, he'd moan about the temperature or the fact it should have a wider bus or that AMD are finally interested in physics acceleration in a proper sense. I'll concede the last point but in my opinion, what we have here is a very good piece of technology that will (like CPUs) only get better in various aspects due to improving manufacturing processes. It beats every other single GPU card with little effort and, when idle, consumes very little juice. The technology is far beyond what RV770 offers and at least, unlike nVidia, ATI seems more interested in driving standards forward. If not for ATI, who's to say we'd have progressed anywhere near this far?

    No company is perfect. No product is perfect. However, to completely slander a company or division just because he buys a competitor's products is misguided to say the least. Just because I own a PC with an AMD CPU, doesn't mean I'm going to berate Intel to high heaven, even if their anti-competitive practices have legitimised such criticism. nVidia makes very good products, and so does ATI. They each have their own strengths and weaknesses, and I'd certainly not be using my 4830 without the continued competition between the two big performance GPU manufacturers; likewise, SiliconDoc's beloved nVidia-powered rig would be a fair bit weaker (without competition, would it even have PhysX? I doubt it).
  • SiliconDoc - Thursday, September 24, 2009 - link

    Well, that was just amazing, and you;re wrong about me not complaining about the 4770 paper launch, you missed it.
    I didn't moan about the temperature, I moaned about the deceptive lies in the review concerning temperatures, that gave ATI a complete pass, and failed to GIVE THE CREDIT DUE THAT NVIDIA DESERVES because of the FACTS, nothing else.
    The article SPUN the facts into a lying cobweb of BS. Juzt like so many red fans do in the posts, and all over the net, and you've done here. It is so hard to MAN UP and admit the ATI cards run hotter ? Is is that bad for you, that you cannot do it ? Certainly the article FAILED to do so, and spun away instead.
    Next, you have this gem " at least, unlike nVidia, ATI seems more interested in driving standards forward."
    ROFLMAO - THIS IS WHAT I'M TALKING ABOUT.
    Here, let me help you, another "banned" secret that the red roosters keep to their chest so their minions can spew crap like you just did: ATI STOLE THE NVIDIA BRIDGE TECHNOLOGY, ATI HAD ONLY A DONGLE OUTSIDE THE CASE, WHILE NVIDIA PROGRESSED TO INTERNAL BRIDGE. AFTER ATI SAW HOW STUPID IT WAS, IT COPIED NVIDIA.
    See, now there's one I'll bet a thousand bucks you never had a clue about.
    I for one, would NEVER CLAIM that either company had the lock on "forwarding technbology", and I IN FACT HAVE NEVER DONE SO, EVER !
    But you red fans spew it all the time. You spew your fanboyisms, in fact you just did, that are absolutely outrageous and outright red leaning lies, period!
    you: " at least, unlike nVidia, ATI seems more interested in driving standards forward...."
    I would like to ask you, how do you explain the never before done MIMD core Nvidia has, and will soon release ? How can you possibly say what you just said ?
    If you'd like to give credit to ATI going with DRR4 and DDR5 first, I would have no problem, but you people DON'T DO THAT. You take it MUCH FURTHER, and claim, as you just did, ATI moves forward and nvidia does not. It's a CONSTANT REFRAIN from you people.
    Did you read the article and actually absorb the OpenCL information ? Did you see Nvidia has an implementation, is "ahead" of ati ? Did you even dare notice that ? If not, how the hell not, other than the biased wording the article has, that speaks to your emotionally charged hate Nvidia mindset :
    "However, to completely slander a company or division just because he buys a competitor's products is misguided to say the least."
    That is NOT TRUE for me, as you stated it, but IT IS TRUE FOR YOU, isn't it ?
    ---
    You in fact SLANDERED Nvidia, by claiming only ATI drives forward tech, or so it seems to you...
    I've merely been pointing out the many statements all about like you just made, and their inherent falsehood!
    ---
    Here next, you pull the ol' switcharoo, and do what you say you won't do, by pointing out you won't do it! roflmao: " doesn't mean I'm going to berate Intel to high heaven, even if their anti-competitive practices have legitimised such criticism.."
    Well, you just did berate them, and just claimed it was justified, cinching home the trashing quickly after you claimed you wouldn't, but have utterly failed to point out a single instance, unlike myself- I INCLUDE the issues and instances, pointing them out imtimately and often in detail, like now.
    LOL you: " I'd certainly not be using my 4830 without ...."
    Well, that shows where you are coming from, but you're still WRONG. If either company dies, the other can move on, and there's very little chance that the company will remain stagnant, since then they won't sell anything, and will die, too.
    The real truth about ATI, which I HAVE pointed out before, is IT FELL OFF THE MAP A FEW YEARS BACK AND ALTHOUGH PRIOR TO THAT TIME WAS COMPETITIVE AND PERHAPS THE VERY BEST, IT CAVED IN...
    After it had it's "dark period" of failure and depair, where Nvidia had the lone top spot, and even produced the still useful and amazing GTX8800 ultimate (with no competition of any note in sight, you failed to notice, even to this day - and claim the EXACT OPPOSITE- because you, a dead brained red, bought the "rebrand whine" lock stock and barrel), ATI "re-emerged", and in fact, doesn't rteally deserve praise for falling off the wagon for a year or two.
    See, that's the truth. The big fat red fib, you liars can stop lying about is the "stagnant technology without competition" whine.
    ATI had all the competition it could ever ask for, and it EPIC FAILED for how many years ? A couple, let's say, or one if you just can't stand the truth, and NVIDIA, not stagnated whatsoever, FLEW AHEAD AND RELEASED THE MASSIVE GTX8800 ULTIMATE.
    So really friend, just stop the lying. That's all I ask. Quit repeating the trashy and easily disproved ati cleche's.
    Ok ?

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