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What do APUs do with their gfx cores when discrete nVidia gfx in use?

N

n_h_x

Junior Member
This has been asked before on various forums but there always seems to be disagreement about the correct answer. (see: http://forums.anandtech.com/showthread.php?t=2414741) Also, since APUs are relatively new and evolving, I'm wondering if the answer has changed.

Context: I have a mid-ish tier HTPC I've also been using for some casual gaming, video editing, etc as my laptop is showing its age more and more. I threw in a GT 730 about a year ago since the onboard gfx were obviously complete crap. It's an FM2+ mobo so I'm stuck with AMD CPUs. Recently I've been finding that my old cheap CPU has been holding me back and upgraded to a A10-7870K for a little extra sauce.

So anyway, I used to have a solid handle on how CPUs work years ago but this APU business is new to me. Are those extra cores useless with discrete graphics, specifically nVidia graphics? Obviously they're not helping graphics processing at all, but are they freeing up computation space at all? Anything I'd notice in gaming, compression calculations, etc? Or is it all just empty space?

Thanks in advance...
 
In theory, in DirectX 12 games the developer could use your IGP for something. In DirectX 11 (and all DirectX 12 games so far) it does nothing.
 
n_h_x said:
Obviously they're not helping graphics processing at all, but are they freeing up computation space at all? Anything I'd notice in gaming, compression calculations, etc? Or is it all just empty space?

Thanks in advance...
Click to expand...

There are some tasks that you can do with the APU graphics but not much that appeals to the common user,look into GPGPU/openCL.
 
APUs have some pretty awesome potential. Since the GPU is integrated, there's hardly any penalty for off-loading realtime tasks to it, in comparison to doing so with a dGPU. Namely, GPU accelerated physics.

Sure, there are those superfluous PhysX effects (e.g, Fallout 4 bullet debris), but don't games run the important stuff (player/NPC <> object collision) on the CPU?

When APUs get beefy, imagine all the sweet HW accelerated physics we'll see. Proper muscle animation, non-faux destruction, seamless navmesh generation, HW accelerated dynamic batching, etc.

God damn, that sounds pretty sweet.
 
LTC8K6 said:
The 7870K graphics might be faster than the GT730, depending on which 730 you have and your ram setup.
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Thanks for the tip. I was actually wondering about this.

I don't expect to be upgrading the graphics card any time soon (having just bought the CPU and now I probably need to drop another ~$40 on a powerful low profile FM2+ socket cooler, since the stock one doesn't even fit in my mini-ITX case).

But I will test performance with/without the GPU if I get around to it (uninstalling / reinstalling the drivers will be a bit of a bitch). If it's pretty much equivalent I'll probably take the discrete card out, if only to get rid of the fan noise.

Thanks to everyone for the insight.

Quick edit: It's this card (http://www.amazon.com/EVGA-GeForce-...psc=1&redirect=true&ref_=od_aui_detailpages01) by the way
 
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7870K 512:32:8 866 MHz with ddr3-2133 ram
GT730 384:32:8 902 Mhz with Gddr5 ram

To get the best out of the 7870K graphics you'd want ddr3-2133 ram in dual channel mode on your mobo.
 
The more I think about it, the more dumb I feel for ever buying an nVidia card for this mobo. Back when I first got it I guess I had thought the APU thing was more of an advertising gimmick. Pretty sure I'll be springing for this guy (http://www.newegg.com/Product/Produ...=radeon_r7_low_profile-_-14-150-713-_-Product) and seeing what I can recoup from the 730 on eBay. So, uh, hit me up if you're looking for a lightly used GT 730 😀.

Thanks again everyone.
 
If you were going to add another low-cost video card, you should've gone for a Radeon R7 250 so it would chain up with the IGP and almost double your graphics performance.

In fact, if you can find someone willing to trade (plus cash?), I'd still do so.
 
He said "casual gaming", though.

If he is into even moderate gaming, then he needs more than a GT730.
 
Light gaming especially,like LeagueofLegends, CS:GO etc, will benefit from higher Ghz way more then from crossfire, which will not even work on a lot of "light gaming" titles.
 
Dual Graphics doesn't work very well, or at least it didn't last time I read the reviews of it. It's better to use the APU only, or not at all, because even though framerates go up with dual graphics, the delivery of them is not spaced very well and result in very "choppy" gameplay.
 
Blue_Max said:
If you were going to add another low-cost video card, you should've gone for a Radeon R7 250 so it would chain up with the IGP and almost double your graphics performance.

In fact, if you can find someone willing to trade (plus cash?), I'd still do so.
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Yeah, that's what I'm going for. Already on order though...

Re: types of gaming... I don't really know about casual vs moderate or anything, but I'm used to playing things on low spec. Currently w/ the CPU upgrade and the GT 730 it's a pretty huge bump from before, I think because switching from an FM2 to an FM2+ CPU allowed the card to run at PCIE 3 spec properly when it could only run at PCIE 2 with the FM2 chip due to motherboard design (something I only dug up recently). Skyrim runs very smoothly at 720p with medium-high settings (I could probably bump to 1080p but 720p with some AA looks nicer in my opinion). Unreal Tournament 4 is mostly smooth as butter on medium settings at 1080p... that's kind of all I've been playing lately.

If it benchmarks faster with the new GPU in, I'll keep it, if not I'll return it.

Dual Graphics doesn't work very well, or at least it didn't last time I read the reviews of it. It's better to use the APU only, or not at all, because even though framerates go up with dual graphics, the delivery of them is not spaced very well and result in very "choppy" gameplay.
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Interesting... I guess I'll find out soon!
 
Here is Tom's review:

http://www.tomshardware.com/reviews/dual-graphics-crossfire-benchmark,3583.html

There's a disconnect between the higher frame rates reported in Fraps and the what you actually see when you capture the DVI port's output. This is a feature AMD has been talking about for almost two years now. Dual Graphics should be mature. We're not sure how many mainstream gamers purchased a graphics card to go along with their Llano-, Trinity-, and Richland-based APUs, believing that they'd get a notably better experience, but from what we're seeing, those additional investments are largely going to waste.

Yes, Fraps is telling us that the average frame rates are notably higher. However, this very conundrum was what inspired FCAT in the first place. If the software is counting every dropped and runt frame toward Dual Graphics' average frame rate, then you're getting absolutely no benefit from pieces of frames like the one pictured that are artificially inflating performance.
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EDIT: It's possible that things have changed since this article was written, but I wouldn't hold my breath.
 
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Pretty damning, although that was a solid two and a half years ago. (Crimson was supposedly a big step forward in functionality right?) I'm very interested to see how things play out when I get my hands on the new card.
 
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