Nvidia 675MX or 680 MX for FCP X on iMac?

I'm not very familiar with how FCPX optimizes GPU usage, though I've read that a faster GPU will indeed increase export times to codecs such as h264. I'm not sure if it will do much for the actual editing experience, however.

If you're getting into 3D rendering, definitely, yes, go with the faster GPU. It will significantly increase your render time if your software is CUDA enabled.

Just a word of warning about your RAM upgrade: the new iMacs are extremely difficult to get apart. The glass is glued to the body so you need to take a heat gun and guitar picks to it to pry it open. You then have to take out most of the internal components because the RAM is on the back side of the motherboard, not the screen side. When you put it all back together, you're going to need to have some good adhesive tape on hand to replace the adhesive you destroyed getting the computer open. Granted, this is what is known about the 21.5" model, which is the only one that has shipped so far, so if you're lucky, the 27" will be much better. I wouldn't get my hopes up though. http://www.ifixit.com/Teardown/iMac+Intel+21.5-Inch+EMC+2544+Teardown/11936/1

hdeane said:

On a new iMac 27" what difference will the nvidia 680mx make over the 675mx, particularly for Final Cut Pro X?


I am looking to purchase a new 27” iMac, a key use of which will be editing a significant amount of home movies – well over 100 hours. I will be using Final Cut Pro X. I expect that I will expand into more advanced movie editing after I complete this task.

I will be getting the i7 3.4ghz processor and the Fusion Drive on a 27" iMac. It will have 24GB of RAM, the 8GB it comes with and 16GB I will add.

I will also be managing a fairly large (200GB) Aperture library, but my editing needs are nowhere near professional.

I will be doing a lot of video conversion using Handbrake, but I believe I have that covered with the processor upgrade.

I am not a gamer, preferring to leave that to my sons. (I couldn’t hope to compete).

{Edit: I will also be moving into more 3D modelling and from reading some posts I think that may push more towards the 680}

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For Final Cut Pro X, you will experience little in the way of performance boosts, though that's highly dependent on what features you use. If you're simply cutting footage together, then you will notice minimal (if any) boosts with the faster card. Certainly not enough to justify the sticker price on the upgrade. If you do color correction, then you will absolutely appreciate the difference.

For 3-D modeling, the better card will likely serve you noticeably better. Really, no matter what you do, the better card will likely extend the life of your machine, so if you can afford it, I say go with it. Plus, it's not like you have the luxury of upgrading later.

As for RAM, unlike the 21.5" iMac, which lacks user-accessible RAM, the 27" iMac has a user-accessible compartment for the RAM. I'd say max that sucker out at 32GB when you can, just don't do it from Apple. Leave RAM at the stock 8GB and upgrade from there. (Though to be safe, I'd say hold onto your factory RAM, even if you're not actually going to use it.)

jonjiv said:

Just a word of warning about your RAM upgrade: the new iMacs are extremely difficult to get apart. The glass is glued to the body so you need to take a heat gun and guitar picks to it to pry it open. You then have to take out most of the internal components because the RAM is on the back side of the motherboard, not the screen side. When you put it all back together, you're going to need to have some good adhesive tape on hand to replace the adhesive you destroyed getting the computer open. Granted, this is what is known about the 21.5" model, which is the only one that has shipped so far, so if you're lucky, the 27" will be much better. I wouldn't get my hopes up though. http://www.ifixit.com/Teardown/iMac+Intel+21.5-Inch+EMC+2544+Teardown/11936/1

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The new 27" iMac has user-accessible RAM. Apple even states this on their iMac page. Only the 21.5" iMac doesn't. You don't need to pry the display off and get it stuck back on in order to access the RAM on the 27" iMac.

Is there a difference in the i5 and i7 when it comes to using final cut?

jonjiv said:

If you're getting into 3D rendering, definitely, yes, go with the faster GPU. It will significantly increase your render time if your software is CUDA enabled.

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Assuming you meant "decrease," this isn't true. Aside from a future version of Vray, the GPU has very little effect on render time. The largest benefit you will see from a better GPU is frame rate and smoothness in the editor, as well as increased speed when calculating simulations.

The act of rendering itself is primarily improved by CPU and RAM. Regardless, the point still stands that a better GPU is better for 3D, just not when render time comes around.

12dylan34 said:

The act of rendering itself is primarily improved by CPU and RAM. Regardless, the point still stands that a better GPU is better for 3D, just not when render time comes around.

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I stand corrected, twice! The latest version of Blender supports CUDA enabled rendering, which is why I was under the impression that it would decrease render times. Some people have claimed rendering is faster using this feature. I haven't been able to test this out since none of my workstations have CUDA video cards.

MacDarcy said:

Is there a difference in the i5 and i7 when it comes to using final cut?

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Yes, Final Cut will use the extra cores on the i7 (8 vs 4) which will affect rendering times primarily.

12dylan34 said:

Assuming you meant "decrease," this isn't true. Aside from a future version of Vray, the GPU has very little effect on render time. The largest benefit you will see from a better GPU is frame rate and smoothness in the editor, as well as increased speed when calculating simulations.

The act of rendering itself is primarily improved by CPU and RAM. Regardless, the point still stands that a better GPU is better for 3D, just not when render time comes around.

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I am sorry, but you are far from correct on your comment. There are renders that indeed use GPU acceleration to better the render time, Indigo Renderer being one of them. The faster the GPU, the better rendering time you get.