OpenCL with Mac Pro : on researcher/developer view

Discussion in 'Mac Pro' started by Amethyst, Jun 8, 2009.

  1. Amethyst macrumors 6502a

    Aug 8, 2006
    1) from wwdc latest information, Mac pro user will have only 3 Apple official option OpenCL that is : GeForce 8800 GT, GeForce GT 120 and Radeon 4870

    2) but I think GTX285 and FX4800 will support too. (At least final ver. of Snow leopard)

    3) Assume you want many core the best selection from 1) & 2) is ATI Radeon 4870 because it has 800 stream processor. GTX 285 have 240

    4) Assume you want memory speed the best selection from 1) & 2) is ATI Radeon 4870 again because it GDDR5 (but i can't confidentally confirm it when 4870 have lower memory speed and lower memory bandwidth)
  2. VirtualRain macrumors 603


    Aug 1, 2008
    Vancouver, BC

    While I'm not informed enough to know the specifics, I'm fairly certain that the stream processors in ATI and Nvidia products are not an apples-to-apples comparison. I would not base any assumptions on OpenCL performance on the # of stream processors across vendors. Within vendors, sure.
  3. Amethyst thread starter macrumors 6502a

    Aug 8, 2006
    may be i wrote this theads a few hasten,

    with my experience it can't tell which one is better before you testing it.

    but this theads it come form some info on openCL tech brief that tell me about openCL kernel that it look like intensive use stream processing, that make me think it will be faster when you use many core.
  4. Subkultured macrumors newbie

    May 6, 2009
    So, the ATI Radeon HD 4870 will support OpenCL in Snow Leopard, correct? Don't want to make a horrid mistake before jumping into this investment, haha!
  5. J the Ninja macrumors 68000

    Jul 14, 2008
    GDDR5 isn't necessarily better, you have to look at clock and bus width, namely that the 285 has a MUCH wider memory bus than the 4870 does, but with a far lower effective clock due to lacking the QDR bus of GDDR5.
  6. t0mat0 macrumors 603


    Aug 29, 2006
    Seeing as Snow Leopard is coming in September, and Nvidia is having a few events around that time, you might well see some new info for products that work with the Mac Pro.
  7. 10THzMac macrumors 6502

    Dec 17, 2007
    Early OpenCL examples worked nicely on 8800. We should find out over next few months how well it works on 285, Quadro and non-Nvidia GPUs. CUDA already OK on 285 under MacOS so it is hard to imagine the Nvidia cards won't be OK under OpenCL. If it is really going to be "Open" it should work on all these GPUs. Having proper GPUs like the 285 with double precision computation and good number of cores opens the door for all kinds of fast apps. The 285 goes more than twice as fast as 8800 under CUDA under 10.5.7, based on a simple NVIDIA multi-GPU Monte Carlo example, at a similar clock speed, which is consistent with number of cores.

    If you apply to Nvidia for developer access and are successful, you can get access to a bunch of OpenCL examples to play with.

    You can see OpenGL benchmark and CUDA deviceQuery output for a PC 285 at my post here:
  8. product26 macrumors 6502a


    May 30, 2005
    anybody want to buy a nice lil X1900xt? j/k

    If it is supported I will be getting a pc 8800gt and flashing it for sure.
    I have that exact card in my hackintosh and it performs nicely.
  9. OZMP macrumors 6502

    Feb 18, 2008

    Hey mate,
    How good is it with the 8800? as I don't think I can justify the $AUD700 That Apple wants for the 4870... maybe a reflashed PC card but prefer to keep my machine proper :apple:

  10. 10THzMac macrumors 6502

    Dec 17, 2007
    Until the official release of Snow Leopard it is awkward to reveal details of the operation of OpenCL. At the risk of stating the obvious

    (i) the performance is consistent with it having 112 cores vs the 240 of a card like the 285 - the latter does some basic maths of simulation just over twice as fast as an 8800 at the same clock speed

    (ii) It does not have double precision capability (single only)

    So it is OK if not blazingly fast as long as you only want single precision, which will be fine for a lot of video and games development.

    The other thing to be careful about is to make sure you have an 8800 that perfectly mimics the Apple version. A properly ROM flashed version will probably be OK, but I am just being careful based on some very recent CUDA experience where PC cards in the 200 series behave a bit inconsistently. The situation with the 8800 is by now a lot better understood so you will probably be OK.
  11. OZMP macrumors 6502

    Feb 18, 2008
    Thanks, I did not realize that there was such a large difference, I have a genuine :apple: 8800, might look at getting a 4870 from the US to save a few hundred.

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