Oculus Rift CPU Benchmark – DiRT Rally (AMD R7 1700 vs. Intel i7-7700K)
We’re starting with Oculus Rift first, then moving to the Vive. Our Rift games include DiRT Rally and Elite: Dangerous. We’re testing DiRT Rally configured to High settings and with advanced blending enabled. This first set of charts will contain all the data we have, while subsequent games will only contain head-to-head data. For all of it, check the article linked below.
Please read the “How to Read the Charts” section on the first page of this article.
Let’s start with the R7 1700 CPU at stock settings.
With everything explained, let’s start with data analysis.
DiRT Rally, Oculus Rift: AMD R7 1700 Stock
For this chart, we’re seeing the R7 1700 encounters a few dropped frames, or frames that were synthesized by updating head tracking and position (without a full update to the scene). Our video component of this review contains video playback of the hardware capture for this run, if you’d like to see the experience. The experience overall is smooth, and the dropped and synthetic frames go unnoticed during use. We don’t have enough to detect as a human, though we can detect it with tools.
We’ll show average frametimes and unconstrained FPS at the end of this charted section.
DiRT Rally, Oculus Rift: AMD R7 1700 Overclocked
Next, the R7 1700 OC shows mostly the same performance, with one large drop at the end of the capture. The time to deliver frames is now shorter with the 3.9GHz overclock, but there’s no major difference in user experience.
DiRT Rally, Oculus Rift: AMD R7 1700 Stock vs. Overclocked
This next chart shows the 1700 stock and overclocked at the same time, where we can observe that the red line – representing the overclocked values – is consistently faster in frame delivery than the yellow line, or the stock 1700. We are generally around 10ms for both devices, but will show this value more explicitly in a moment.
DiRT Rally, Oculus Rift: Intel i7-7700K Stock
Here’s the Intel i7-7700K CPU with its stock settings. The Intel CPU has a few drops but, just like the R7 chip, these are not appreciable to the user. Frametimes are closer to the 8-9ms mark, with the hardware frametime spikes validating the software measurements at exactly the same times.
The video component of this review contains gameplay playback of this capture. You’ll notice there that user experience is smooth and without any significant or noticeable hitches.
DiRT Rally, Oculus Rift: Intel i7-7700K Overclocked
Here are the overclocked values with both SW + HW capture going concurrently.
Both CPUs can deliver a smooth experience which is subjectively, to the human eye, the same – but let’s look at how they compare objectively.
DiRT Rally, Oculus Rift: Intel i7-7700K vs. AMD R7 1700 (Stock)
Here’s a chart showing the 1700 and 7700K head-to-head at stock frequencies. Because we have standardized this benchmark with the same head movements, we can see that the frametime spikes generally align between both the 1700 and 7700K. Intel is faster overall in frametime delivery in this test, with each CPU dropping fewer than 20 frames throughout the entire run. It’s not until drop frames are significantly greater on one config that we’d notice them, so for all intents and purposes, the experience on each CPU is the same. That said, Intel is faster in its frametimes on this particular title, and experiences shorter spikes when the going gets tough.
One more frametime chart, then we’ll look at the bar graphs.
DiRT Rally, Oculus Rift: Intel i7-7700K vs. AMD R7 1700 (OC)
Here, we’re looking at the two CPUs overclocked, with Intel at 4.9GHz and AMD at 3.9GHz. Both overclocks are achievable on the majority of the respective chips. The drop frames are similar again, with the experience being effectively equivalent. AMD is closer to the 11-13ms cut-off window, but still within bounds. Interestingly, Intel loses ground in the overclocking test compared to the stock benchmarks.
Let’s get a bar graph on the screen for better illustration.
DiRT Rally, Oculus Rift: Bar Charts
This chart plots delivered FPS to the headset, which is the most important metric, then drop frames as the second most important metric, and unconstrained FPS as a calculation. Unconstrained FPS is an imperfect prediction of how many frames would be delivered per second given an HMD without VSync forced, since the HMDs refresh at a hard 90Hz. This is calculated by taking 1000ms and dividing it by the average frametime, which is done in the new FCAT VR tool automatically.
The two hard metrics are Delivered FPS – which we can validate with an effectively infallible hardware capture – and drop frames, also validated by hardware capture. Drop frames are an absolute measure in total frame count over the test period, which is 60-seconds. At 90Hz, a 60s test pass will produce 5400 refresh intervals on the headset.
In this chart for DiRT Rally, we immediately see that both the 1700 and 7700K are capable of delivering 90FPS to the headset. That’s what we want. The drop frames have a range of 8, going from 3 to 11 drop frames per test pass. As we saw in our previous charts, the drop frames are not clustered tightly enough to be noticeable by the user. In the absolute worst case, the R7 1700 encounters 11 drop frames over its 5400 refresh intervals, yielding 0.2% drop frames for the test period. A user would not notice this, particularly when they’re spaced out over the period.
We next see that unconstrained FPS lands around 135-137 for the i7-7700K, while the R7 1700 is in the 105-115FPS range. Again, this is an extrapolation – we’re still seeing 90 on either device. Let’s look at average frametime.
This shows how that number is calculated. This chart’s scale is set to 12ms, at which point you’ll probably start encountering drop frames, warp misses, or reprojection issues. The 7700K stock and overclocked CPUs perform effectively equally at 7.3 to 7.4ms. The R7 1700 shows a bigger gain from the overclock, just outside tolerances, landing at 8.7ms from 9.54ms. Comparatively, the 7700K stock experiences a 22% reduction in average frametime over the R7 1700 Stock and about 14.8% reduction versus the overclocked R7 1700. Intel loses ground in overclocking advantage, but retains an overall objective lead. The impact of this lead, again, is inconsequential: We still see 90FPS on the headset for each device, and without any significant amount of warp misses or drop frames, performance can be deemed “effectively equivalent.”
Let’s move on to the next game.
Elite: Dangerous, Oculus Rift: AMD R7 1700 Stock & OC
Our frametime hits align again when comparing HW & SW capture to one another, assisting in validation. The interval plots also align with spikes above ~11ms. Comparatively, overclocking on the R7 1700 provides some performance improvement (see: red line generally below yellow line), though we’ll need our bar graphs to visualize the extent of that gain from an overclock. There is no significant count of drop frames or warp misses in this benchmark.
Elite: Dangerous, Oculus Rift: Intel i7-7700K Stock & OC
Overclocking the 7700K doesn’t benefit in a meaningful way for this benchmark. The white and blue lines largely coincide, showing no perceptible difference between test passes (even within variance measures).
Elite: Dangerous, Oculus Rift: AMD R7 1700 vs. Intel i7-7700K (Stock)
This first comparative chart shows the 1700 versus the 7700K, both at stock frequencies. The R7 1700 tends to run slower in average frametime delivery, sometimes running against the limit before we start encountering the Rift’s 11-13ms refresh interval. Again, note that Oculus does some things in the runtime to stretch the 11ms refresh out a little bit. As illustrated in the interval plot at the bottom, the R7 1700 and i7-7700K are dropping and synthesizing a similar amount of frames, with neither appreciably worse than the other. As a user, again, this experience is equal within the confines of human perception.
That said, the difference is statistically significant. You could make an argument that the extra headroom is valuable, but we have not found a scenario yet where we begin encountering noticeable, jarring stuttering on either the 1700 or 7700K. The theoretical argument would be one of future-proofing, but we simply don’t yet have enough data (or years) with VR to know how well such an argument holds up, and so will not be making it. The data is presented largely as-is for these tests.
Elite: Dangerous, Oculus Rift: AMD R7 1700 vs. Intel i7-7700K (OC)
This chart shows that overclocking the R7 1700 tends to close the gap versus Intel, which is also now overclocked. That’s the same as we saw in DiRT Rally – it appears that overclocks don’t benefit Intel quite as much as they’re benefitting AMD here, likely because of the R7’s lower starting frequency.
We’re seeing a range of 6 for the drop frames, from 11 to 17 in the best and worst cases. The i7-7700K OC and i7-7700K stock perform equally, within variance, and further illustrate that VR benchmarking is not yet repeatable enough to analyze with tight margins and firm statements. Even in the worst case of 17 drop frames, we’re still at 0.3% of all frames delivered as dropped, whereas 11 drop frames would be 0.2% -- completely imperceptible to the user. The dropped frames are also dispersed enough to not matter.
With regard to actual delivered frames, we’re at 90FPS for all four tests. Intel holds a lead in unconstrained FPS as it has shorter frame latencies overall, as shown in this next chart. We’re at roughly 8.6ms between the two Intel tests, and at 9.9 to 10.4ms for the AMD tests. 10.41ms is starting to push the limit of what we’re comfortable with, but still delivers a smooth experience in this game. The overclock keeps us reasonably distanced from the 11-13ms mark. There is no perceptible difference between these SKUs, given that all hit the 90FPS delivery mark with insignificant drop frame counts.
Hardware capture playback of this is in the video component of the review.