After several requests and a week’s break from our initial DirectX 12 article, we’re back again with an investigation into Star Swarm DirectX 12 performance scaling on AMD APUs. As our initial article was run on various Intel CPU configurations, this time we’re going to take a look at how performance scales on AMD’s Kaveri APUs, including whether DX12 is much help for the iGPU, and if it can help equalize the single-threaded performance gap been Kaveri and Intel’s Core i3 family.

To keep things simple, this time we’re running everything on either the iGPU or a GeForce GTX 770. Last week we saw how quickly the GPU becomes the bottleneck under Star Swarm when using the DirectX 12 rendering path, and how difficult it is to shift that back to the CPU. And as a reminder, this is an early driver on an early OS running an early DirectX 12 application, so everything here is subject to change.

CPU: AMD A10-7800
AMD A8-7600
Intel i3-4330
Motherboard: GIGABYTE F2A88X-UP4 for AMD
ASUS Maximus VII Impact for Intel
Power Supply: Rosewill Silent Night 500W Platinum
Hard Disk: OCZ Vertex 3 256GB OS SSD
Memory: G.Skill 2x4GB DDR3-2133 9-11-10 for AMD
G.Skill 2x4GB DDR3-1866 9-10-9 at 1600 for Intel
Video Cards: MSI GTX 770 Lightning
Video Drivers: NVIDIA Release 349.56 Beta
AMD Catalyst 15.200 Beta
OS: Windows 10 Technical Preview 2 (Build 9926)


Star Swarm CPU Scaling - Extreme Quality - GeForce GTX 770


Star Swarm CPU Scaling - Mid Quality - GeForce GTX 770

Star Swarm CPU Scaling - Low Quality - GeForce GTX 770

To get right down to business then, are AMD’s APUs able to shift the performance bottleneck on to the GPU under DirectX 12? The short answer is yes. Highlighting just how bad the single-threaded performance disparity between Intel and AMD can be under DirectX 11, what is a clear 50%+ lead for the Core i3 with Extreme and Mid qualities becomes a dead heat as all 3 CPUs are able to keep the GPU fully fed. DirectX 12 provides just the kick that the AMD APU setups need to overcome DirectX 11’s CPU submission bottleneck and push it on to the GPU. Consequently at Extreme quality we see a 64% performance increase for the Core i3, but a 170%+ performance increase for the AMD APUs.

The one exception to this is Low quality mode, where the Core i3 retains its lead. Though initially unexpected, examining the batch count differences between Low and Mid qualities gives us a solid explanation as to what’s going on: low pushes relatively few batches. With Extreme quality pushing average batch counts of 90K and Mid pushing 55K, average batch counts under Low are only 20K. With this relatively low batch count the benefits of DirectX 12 are still present but diminished, leading to the CPU no longer choking on batch submission and the bottleneck shifting elsewhere (likely the simulation itself).

Star Swarm CPU Batch Submission Time - Extreme - GeForce GTX 770

Meanwhile batch submission times are consistent between all 3 CPUs, with everyone dropping down from 30ms+ to around 6ms. The fact that AMD no longer lags Intel in batch submission times at this point is very important for AMD, as it means they’re not struggling with individual thread performance nearly as much under DirectX 12 as they were DirectX 11.

Star Swarm GPU Scaling - Mid Quality

Star Swarm GPU Scaling - Low Quality

Finally, taking a look at how performance scales with our GPUs, the results are unsurprising but none the less positive for AMD. Aside from the GTX 770 – which has the most GPU headroom to spare in the first place – both AMD APUs still see significant performance gains from DirectX 12 despite running into a very quick GPU bottleneck. This simple API switch is still enough to get another 44% out of the A10-7800 and 25% out of the A8-7600. So although DirectX 12 is not going to bring the same kind of massive performance improvements to iGPUs that we’ve seen with dGPUs, in extreme cases such as this it still can be highly beneficial. And this still comes without some of the potential fringe benefits of the API, such as shifting the TDP balance from CPU to GPU in TDP-constrained mobile devices.

Looking at the overall picture, just as with our initial article it’s important not to read too much into these results right now. Star Swarm is first and foremost a best case scenario and demonstration for the batch submission benefits of DirectX 12. And though games will still benefit from DirectX 12, they are unlikely to benefit quite as greatly as they do here, thanks in part to the much greater share of non-rendering tasks a CPU would be burdened with in a real game (simulation, AI, audio, etc.).

But with that in mind, our results from bottlenecking AMD’s APUs point to a clear conclusion. Thanks to DirectX 12’s greatly improved threading capabilities, the new API can greatly close the gap between Intel and AMD CPUs. At least so long as you’re bottlenecking at batch submission.

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  • nissangtr786 - Wednesday, February 18, 2015 - link

    It says its an i3 4330. Anyway finally after 5 or 6 years intel cpus owning in dx11 games amd cpus with dx12 release will finally be able to play games how there gpus intended instead of massive bottlenecks. I seen a lot of people on forums upgrade gpus costing £200-£300 and getting worse performance then people with i3 and a £100 gpu just because of cpu bottleneck and these people don't realise the amd cpu been bottlenecking them just because there cpu isn't utilised 100% while there gpu is pegged at like 20-50%. Good news all round I say as it means no more wasted gpu performance.
  • akamateau - Tuesday, February 24, 2015 - link

    Why buy an nVidia GPU AIB? Just get an AMD APU. It's cheaper than the Intel choice AND you do not need to spend money on a GPU!!!

    If you insist on an Intel IGP then you need the nVidia GPU AIB. That increases your system cost by about $300 over what the same system would cost with the AMD APU.

    Wait until Carrizo hits the bricks. Intel graphics is an embarrassment.
  • akamateau - Monday, February 23, 2015 - link

    I wonder if Anand Tech has the journalistic guts to show the results of i3-4330 WITHOUT the benefit of Geforce 770 AIB?

    I for one want to see just how bad Intel HD IGP really is.

    Even better would be a bench test that shows at what point DOES Intel i3, i5 or i7 compares to AMD A10-7800 running Star Swarm.

    Direct x12 is the best friend that AMD has ever had. All thanks to Mantle.
  • Xailter - Friday, February 13, 2015 - link

    Do you think Carrizo (image compression) 'apparently' boasting up to 2x performance and DX12 reducing the CPU problem; that the next gen APUs will be capable of 1080p 60 fps gaming?

    Maybe not for brand new games but...
  • SaberKOG91 - Friday, February 13, 2015 - link

    Possibly. The combined memory bandwidth savings of DX12 (or Mantle) and texture compression are certainly intriguing. Not to mention the boos that hUMA provides by not needing to copy memory blocks from CPU to GPU regions of RAM.
  • FlushedBubblyJock - Sunday, February 15, 2015 - link

    This puts AMD at further risk, since DX12 is pumping up nVidia cards to mantle performance, thus they will surpass AMD.
  • Alexvrb - Sunday, February 15, 2015 - link

    They were strictly talking about APUs. So it doesn't matter whether they used DX12 or Mantle, both will benefit Carrizo greatly and yeah it may very well achieve decent 1080p gaming at least with the higher-end chips.

    For discrete cards DX12 should be fairly neutral if game developers don't heavily optimize for one architecture (use Nvidia prebuilt middleware, for example). So it really depends on what each company deploys in the coming months and years.
  • akamateau - Tuesday, February 24, 2015 - link

    You don't understand the Benchtest.

    A10-7800 = Intel i3-4330 + nVidia GeForce 770.

    Intel i3-4330 just can not compete with AMD WITHOUT GeForce 770.

    Embarassing for Intel.

    This was the whole point of Mantle: to force Microsoft into evolving Directx11 several generations to be competitive with Mantle.
  • akamateau - Tuesday, February 24, 2015 - link

    Notice how Anand doesn't embarrass Intel by testing i3-4330 without nVidia 770 on-board.
  • HisDivineOrder - Saturday, February 14, 2015 - link


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