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Thread: OpenCL on Apple imac with ATI Radeon HD 4850 is badly broken

  1. #1

    OpenCL on Apple imac with ATI Radeon HD 4850 is badly broken

    I have tested some demos on Snow Leopard (10.6.3). Some work fine but some many examples seem to crash AMD's compiler. Even Apple's own OpenCL_Procedural_Grass demo is crashing. Most of the demos from here: http://davibu.interfree.it/index.html do not work either. (They had to be modified a bit to run on MacOS but most give compiler crashes).

    Can't believe how Apple could push such bad drivers when they are the ones that spearheaded the OpenCL effort

    Anyone knows if this crashing bug is confirmed? Any idea when AMD will fix this? And how soon Apple will push the updates.

  2. #2
    Junior Member
    Join Date
    Sep 2009
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    14

    Re: OpenCL on Apple imac with ATI Radeon HD 4850 is badly broken

    ATI drivers on OS X doesn't implement context sharing between OpenGL and OpenCL, you must check if the Apple gl sharing extension is available.

    And the second issue is because ATI cards doesn't support image 2D and Image 3D, if the kernel
    use this kind of cl memory the kernel cannot be executed.

    It's exactly the same issue on Windows, ATI need to work on their driver but they focused their effort on 5xxx series which is actually not available on Mac....

  3. #3

    Re: OpenCL on Apple imac with ATI Radeon HD 4850 is badly broken

    What? no context sharing either :s. But anyways, that's lack of features. I'm not complaining about that (currently). This is about stability of ATI's compiler. All those crashes occur during kernel compilation. Not during kernel execution. Their compiler is in very bad shape and from what it looks like they are actually using LLVM so, its not like they are developing it from scratch. First time I'm using an ATI GPU and this is my experience *sigh*.

  4. #4
    Junior Member
    Join Date
    Apr 2011
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    1

    Re: OpenCL on Apple imac with ATI Radeon HD 4850 is badly br

    I have been getting the same problems with my 4850. I get strange compilation errors when I try to compile certain kernels. I say strange, because after much testing and fiddling with the kernel, there doesn't seem to be any rhyme or reason to it. It compiles ok if I comment out one of several bits of code, all of which are harmless (trust me, I know; their calls/calculations are repeated in different forms all over my kernel, and I've triple-checked the var names, types, etc).

    Meanwhile, the same kernel compiles fine on another computer with a GeForce GT 120. Is there some way of resolving this?

  5. #5
    Senior Member
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    Toronto, Canada
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    845

    Re: OpenCL on Apple imac with ATI Radeon HD 4850 is badly br

    I would notify Apple's developer support giving them a short kernel that reproduces the issue.
    Disclaimer: Employee of Qualcomm Canada. Any opinions expressed here are personal and do not necessarily reflect the views of my employer. LinkedIn profile.

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