9400M - smart move?

Discussion in 'iMac' started by L0s7man, Mar 4, 2009.

  1. L0s7man macrumors 6502

    Feb 26, 2009
    I was wondering about the whole 9400M in iMac thingie. People are asking themselves where's the benefit of integrated over discrete and frankly, it might be hard to see.

    But one thing occurred to me; the integrated GPU shares the RAM and that can make a difference. While you'd think that it's rather a bad thing (hey, stop stealing my RAM! got get your own you b#(*!), I think it might be for the better.

    How? GPU accelerated computing.

    I've been playing with CUDA lately and however OpenCL turns out to be, the biggest problem will be essentially the same - moving data from RAM to GPU memory. This takes time. Moreover, you have to do it twice!

    Say, you want to multiply two numbers on the GPU. Initially they're somewhere in your main memory. You have to dig them up, transfer them to GPU, multiply and transfer them back again. And graphic cards aren't really designed to do that - normally data comes through one end, and goes out through the other (to the display!).

    If your GPU could simply access this data directly (I think you'd have to do some hardware/bios/software magic to do that), it would make things much nicer ;-D

    I need to look it up. It can be quite interesting.

    Anyone did some CUDA programming?
  2. lewchenko macrumors regular

    Jun 8, 2004
    Im not convinced.

    I think you may be wrong, but I dont have the evidence to back it up. Integrated graphics that steal system memory have one thing in common across their entire history .... poor performance in just about everything you need to do with it.

    Perhaps CUDA will be the exception, but for everything else.. its fail.

    This GPU belongs in laptops... nowhere else. On a desktop.. at these prices... its an insult.

    Just remember that in the PC world, a 9400 graphics card is BOTTOM END BARGAIN BASEMENT material. I hear people using UT2004 as a benchmark to measure whether it performs well...

    erm.. its now 2009 people. Its weird how the mac GPU's lag behind so badly. Im sure Apple could do better.. wonder why they dont ? Their beloved margins perhaps ?
  3. L0s7man thread starter macrumors 6502

    Feb 26, 2009
    Nvidia design is quite different to what Intel offered throughout the years. Nvidia GPU core is a part of the motherboard chipset. In Intel design, it was separate, just hooking up to the RAM.

    So, there's quite a difference. (note: I don't remember the exact design; you'd have to dig it up). That's why 9400M kicks ass when compared to anything Intel ever did.

    As for performance: NOT FOR GAMES. It doesn't make much sense for games. When you're playing games, GPU is used to compute stuff that goes to your screen, and your CPU does the rest (AI, pathfinding, etc). The goal is to speed up normal applications - Photoshop, Video editing, etc.

    Imagine you have some 1080p video and you want to do something with it (I don't do video editing, so I don't know what :p) Say you want to do antishake or something. It makes sense to copy it over to the GPU, wait for GPU to do the job (which will do it like 128 times faster than CPU) and copy it back to your RAM for you to use it.

    But if you have lot's of small, on the fly operations, copying it back and forth takes too much time and it simply makes no sense.
  4. Hellhammer Moderator


    Staff Member

    Dec 10, 2008
    I can't understand why Apple uses so crappy GPUs. Macs are powerful from everywhere else than GPU. I just checked few gaming PCs and they all had ~2.5GHz dual-core processors and nVidia GTX260s with price tag of 799€. It's stupid that Apple "ruins" their computers with bad GPUs :(
  5. edgew8 macrumors regular


    Dec 8, 2008
    I dont like the move but I am not going to buy one so I wont whine anymore about it. I will concede that I do not know what goes on behind closed doors at apple. Maybe the 9400m is more reliable than the ati's and will ease the cost of repairs done buy apple and extend the life of the iMac and have it spend more time on your desk instead of the repair shop. Maybe the 9400m is better at 2d performing instead of trying to make the iMac something it is not ( a 3d gaming machine) and is improving the things it actually was intended for.

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