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OpenCL In Action: Post-Processing Apps, Accelerated

Benchmark Results: vReveal On The A8-3850 With Discrete Graphics

Now we edge closer to the big question of the day: is AMD’s APU platform capable enough to tackle the same demanding tasks for which we usually recommend FX and Core i5/i7 processors? Let’s warm up by examining how the CPU component of the chip fares when backed by discrete graphics.

In this context, looking at our CPU-only software results should be the most telling. Sure enough, we see the non-accelerated 480p test shows that the FX-8150 enjoys 13% lower CPU utilization compared to the A8, while the 1080p clip lets the FX cruise around at 22% lower utilization. With an almost 70% load on the A8, we’d be reluctant to even attempt this operation while multitasking in the real world.

However, notice that utilization also leaps on the A8 even when GPU acceleration is turned on. Whereas the 1080p load on our FX-8150 and Radeon HD 5870 platform was 10%, it jumps to 38% on an A8-3850 and Radeon HD 5870. This is the most compelling evidence that, even in the world of OpenCL and hardware-based acceleration, it still takes a balanced combination of CPU and GPU to yield the best experience. Offloading a task doesn't mean it's completely alleviated. Clearly, MotionDSP still relies on a capable host processor for part of its workflow.

With only one effect active, our job still renders at full speed in all cases except 1080p in software mode. Despite the significant difference in CPU utilization, the net effect on render performance between our two CPUs is only 6%.

With six effects enabled, we again see the FX offer a slight utilization advantage over the A8 when running in software. But given that all numbers are at least 67%, we’d say the benefits of the FX here are nominal.

With GPU-assist turned on, all of our utilization percentages plummet. However, the A8 still shows twice as much utilization as the FX, predictably indicating that the tasks handled by each host processor hit AMD's A8 harder than its flagship FX.

Reinforcing the point, we see the A8 take a 25% render speed hit compared to the FX when relying on a Radeon HD 5870 for acceleration. This is interesting because, while the CPU utilization numbers seem unkind to our FX in a CPU comparison, these real-world numbers show that the FX can still yield a significant time savings in high-load scenarios.

No surprises here. The A8 APU incurs 15% to 20% higher utilization than the FX.

More important, while the FX-8150 and Radeon HD 7970 combination demonstrates a 3.5x CPU utilization benefit from enabling graphics acceleration at 1080p, the A8-3850 enjoys a less than 2x benefit. Again, we see the pitfall of putting too-powerful of a graphics card with a processor that can't always keep up. Balance is critical when you want to maximize performance, and it really takes a higher-end CPU to fully exploit what a potent graphics card offers.

The 1080p accelerated test shows our A8 running at 27% utilization with a Radeon HD 5870 plugged in. It jumps to 40% with a Radeon HD 7970 installed. And yet, when we look at render performance, the Radeon HD 7970 has a 24% advantage, managing near-real-time output. What's all of that mean?

It'd appear that the 7970 is doing more work than the 5870, in turn creating a larger workload for the A8. Although you end up seeing higher CPU utilization, the end result is an experience that's closer to ideal. That is to say, close to real-time rendering is possible here where it wasn't on the Radeon HD 5870.