Last week NVIDIA released their first set of end-user OpenCL drivers. Previously OpenCL drivers had only been available for developers on the NVIDIA side of things, and this continues to be the case on the AMD side of things. With NVIDIA’s driver release, the launch of AMD’s 5800 series, and some recent developments with OpenCL, this is a good time to recap the current state of OpenCL, and what has changed since our OpenCL introductory article from last year.

A CPU & GPU Framework

Although we commonly talk about OpenCL alongside GPUs, it’s technically a hardware agnostic parallel programming framework. Any device implementing OpenCL should be cable of running any OpenCL kernel, so long as the developers take in to account querying the host device ahead of time as to not spawn too many threads at once. And while GPUs (being the parallel beasts that they are) are the primary focus, OpenCL is also intended for use on CPUs and more exotic processors such as the Cell BE and DSPs.

What this means is that when it comes to discussing the use of OpenCL on computers, we have two things to focus on. Not only is there the use of OpenCL on the GPU, but there’s the use of OpenCL on CPUs. If Khronos has their way, then OpenCL will be a commonly used framework for CPUs both to take better advantage of multi-core CPUs (8 threaded i7 anyone?) and as a fallback mechanism for when OpenCL isn’t available on a GPU.

This also makes things tricky when it comes to who is responsible for what. AMD for example, in making both GPUs and CPUs, is writing drivers for both. They are currently sampling their CPU driver as part of their latest Stream SDK (even if it is a GPU programming SDK), and their entire CPU+GPU driver set has been submitted to the Khronos group for certification.

NVIDIA on the other hand is not a CPU manufacturer (Tegra aside), so they are only responsible for having a GPU OpenCL driver, which is what they have been giving to developers for months. They have submitted it to Khronos and it has been certified, and as we mentioned they have released it to the public as of last week. NVIDIA is not responsible for a CPU driver, and as such they are reliant on AMD and Intel for OpenCL CPU drivers. AMD likes to pick at NVIDIA for this, but ultimately it’s not going to matter once everyone finally gets up to speed.

Intel thus far is the laggard; they do not have an OpenCL implementation in any kind of public testing, for either CPUs or GPUs. For AMD GPU users this won’t be an issue, since AMD’s CPU driver will work on Intel CPUs as well. For NVIDIA GPU users with Intel CPUs, they'll be waiting on Intel for a CPU driver. Do note however that a CPU driver isn't required to use OpenCL on a GPU, and indeed we expect the first significant OpenCL applications to be intended to run solely on GPUs anyhow. So it's not a bad situation for NVIDIA, it's just one that needs to be solved sooner than later.

OpenCL ICD: Coming Soon

Unfortunately matters are made particularly complex by the fact that on Windows and Linux, writing an OpenCL program right now requires linking against a vendor-specific OpenCL driver. The code itself is still cross-platform/cross-device, but in terms of compiling and linking OpenCL has not been fully abstracted. It’s not yet at the point where it’s possible to write and run a single Windows/Linux program that will work with any OpenCL device. It would be the equivalent of requiring an OpenGL game (e.g. Quake) to have a different binary for each GPU vendor’s drivers.

The solution to this problem is that OpenCL needs an Installable Client Driver (ICD), just like OpenGL does. With an ICD developers can link against that, and it will handle the duties of passing things off to vendor-specific drivers. However an ICD isn’t ready yet, and in fact we don’t know when it will be ready. NVIDIA - who chairs the OpenCL working group - tells us that the WG is “driving to get an ICD implementation released as quickly as possible”, but with no timetable attached to that. The effort right now appears to be on getting more OpenCL 1.0 implementations certified (NV is certified, AMD is in progress), with an ICD to follow.

Meanwhile Apple, in the traditional Apple manner, has simply done a runaround on the whole issue. When it comes to drivers they shipped Snow Leopard with their own OpenCL CPU driver, and they have GPU drivers for both AMD and NVIDIA cards. Their OpenCL framework doesn’t have an ICD per-say, but it has features that allow developers to query for devices and use any they like. It effectively accomplishes the same thing, but it’s only of use when writing programs against Apple’s framework. But to Apple’s credit, as of this moment they currently have the only complete OpenCL platform, offering CPU+GPU development and execution with a full degree of abstraction.

What GPUs Will Support OpenCL

One final matter is what GPUs will support OpenCL. While OpenCL is based around the hardware aspects of DirectX10-class hardware, being DX10 compliant isn’t enough. Even among NVIDIA and AMD, there will be some DX10 hardware that won’t support OpenCL.

NVIDIA: Anything that runs CUDA will run OpenCL. In practice, this means anything in the 8-series or later that has 256MB or more of VRAM. NVIDIA has a full list here.

AMD: AMD will only be supporting OpenCL on the 4000 series and later. Presumably there was some feature in the OpenCL 1.0 specification that AMD didn’t implement until the 4000 series, which NVIDIA had since the launch of the 8-series. Given that AMD is giving Brook+ the heave-ho in favor of OpenCL, this will mean that there’s going to continue to be a limited selection of GPGPU applications that work on these cards as compared to the 4000 series and later.

End-User Drivers

Finally to wrap this up, we have the catalyst of this story: drivers. As we previously mentioned, NVIDIA released their OpenCL-enabled 190.89 drivers to the public last week, which we’re happy to see even if the applications themselves aren’t quite ready. This driver release was a special release outside of NVIDIA’s mainline driver releases however, and as such they’re already out of date. NVIDIA released their 191.07 WHQL-certified driver set yesterday, and these drivers don’t include OpenCL support. So while NVIDIA is shipping an OpenCL driver for both developers and end-users, it’s going to be a bit longer until it shows up in a regular release.

AMD meanwhile is still in a developer-only beta, which makes sense given that they’re still waiting on certification. The estimates we’ve heard is that the process takes a month, so with AMD having submitted their drivers early last month, they should be certified soon if everything went well.



View All Comments

  • tweakoz - Wednesday, October 21, 2009 - link

    What if you are trying to use multiple devices (from different vendors) simulultaneously?

  • Scali - Wednesday, October 21, 2009 - link

    That's the only time when you'll need to have an ICD.
    However, in most cases just a single device will be fine. Developers or end-users wanting to use OpenCL on a single GPU (or a set of GPUs from the same vendor) is by far the most common scenario.
  • Zool - Wednesday, October 07, 2009 - link

    First nvidias drivers are for gt200 and lower and just gpu-s so its no reason for nvidia not to hawe drivers first.
    Second amd-s new gpu had come out this month so its obvious that they waited with the drivers so they hawe everything in one.
    Also they hawe cpu+gpu support and i think they prepared it with CPU and GPU merge in mind later on.
  • Scali - Wednesday, October 07, 2009 - link

    AMD still doesn't have GPU drivers for OpenCL at all.
    And they currently only support DirectCompute on the HD5800-series. The 4000-series should also support DirectCompute CS4.1, but no drivers in sight.
    There's no reason for AMD to delay 4000-series support for newer hardware. And there's even less reason for AMD not to support them even after releasing newer GPUs.
    Apparently nVidia supports their existing customers much better. They too have a new GPU upcoming, but that didn't stop them from supporting all their existing customers, all the way back to the 3-year old 8800-series. AMD 'only' has to support the 4000-series, as the other hardware isn't capable anyway, but still, nothing.
  • Zool - Wednesday, October 07, 2009 - link

    Testing and certificating drivers takes quite a time. I dont see to much reason to make them first for 4k series than cpu-s and than also for the whole 5K series (which is actualy quite more cards than 5870 and 5850).
    It would make much more sense to make it at once. Which nvidia also did but with the 1 year old GPU as their latest.
  • Scali - Wednesday, October 07, 2009 - link

    Yes, testing and certifying drivers takes time. That's no excuse though, is it? nVidia has to go through the same process, and nVidia actually supports 3 major series of GPUs (G80, G92 and GT200) in their drivers, AMD only has to do two (RV770 and RV870).

    Besides, especially in the case of OpenCL, that has NOTHING to do with new GPUs. The OpenCL project started a long time ago, and AMD promised us drivers in the first half of 2009.
    And even now that their new GPU is on the market, there STILL aren't any OpenCL drivers. AMD just failed to deliver on their promises.

    And if I owned an HD4870, what do I care about the new GPU? Why should I wait? I just want the OpenCL support that AMD promised me. Especially when AMD shouts their mouth off about OpenCL and GPU-accelerated physics in the press. nVidia owners don't even NEED to wait for OpenCL, because they can already get accelerated physics and such through Cuda. Yet they get OpenCL before AMD owners do aswell. AMD should stop marketing vapourware and start supporting their customers.
  • tamalero - Wednesday, October 07, 2009 - link

    I'm the only one that seen the news about Fermi board mockup that wasnt even a real Fermi board in the first place?
    talk about vaporware o_O
  • Amiga500 - Wednesday, October 07, 2009 - link

    I think its a fair guess to say you are affiliated with Nvidia.

    It'll come in time. I for one, would rather wait a bit for drivers that encompass both the CPU and GPU.
  • Scali - Wednesday, October 07, 2009 - link

    Nope, completely wrong guess. Reply
  • Titanius - Wednesday, October 07, 2009 - link

    If I had to take a guess at it, you are SiliconDoc the annoying commentor from the Fermi article with a different name and using less caps locks...did you finally calm down?

    Oh and BTW, WE DON'T CARE who came out first with the drivers, they will eventually both have it.

    My understanding of AMD's lateness to the "party" is because they were busy launching the HD5xxx series cards and didn't have the same "free" time on their hands as NVIDIA has with their phantom GT300/Fermi release (I'm saying phantom because it has been talked about but there is no final product in testing (I don't refer to the first silicons of a new product as final).

    NVIDIA came first for OpenCL, but AMD came first for DirectX 11, GET OVER IT!

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