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GPU Benchmarks? Try to See the Complete Picture…

GPU Benchmarks? Try to See the Complete Picture…
by Eric Esteve on 10-15-2014 at 3:29 am

We all know benchmarks, but do we really understand benchmark results? Benchmark users should always look beyond the simple score when making in-depth technical analysis and request to see all the facts. There are many graphics benchmarks to choose from but let’s name today these three below:

3DMark Ice Stormfrom Futuremark
GFXBench 3.0from Kishonti
Basemark Xfrom Rightware

We tend to look first at raw GFLOPS results, but we should also analyze performance in both GFLOPS/mm2 and GFLOPS/mW. A smartphone user will probably don’t care about GFLOPS/mm2, even if he will certainly care about the price of the phone, and both are certainly linked: just take a look at the Apple A8 layout. The A8 has been processed in 20nm, integrating Quad-Core GPU from Imagination (the PowerVR…). The Quad-Core GPU and shared GPU logic represent 22% of the chip area (89 mm[SUP]2[/SUP]), the impact on chip, then smartphone price is indisputable! But Apple and iPhone 6 users will certainly care about GFLOPS/mW. If you look at Graphic benchmark results, you should care about power efficiency, too. And we will see that you may have to look further than to the raw GFLOPS results.

Benchmarks results are expressed in term of Triangles, Pixels and GFLOPS:

Real world applications have modest triangles rate requirements; moreover, high triangle rates in mobile quickly become memory bandwidth limited way before they turn out to be GPU-limited. In fact, on most GPUs today, triangle throughput is no longer a problem – or even a relevant metric. Mobile GPUs today can easily support 100 to 200 million triangles per second (MTri/s), providing more than enough resources for real world cases.

Pixels and Texcel
Pixel rates on the other hand are probably the most important metric for all market segments and typical usage scenarios. User interfaces or browser running at 60 fps are all about pushing textured pixels. If you are looking for an easy top level requirement calculation, the formula below offers you the headline million pixels per second (MPix/s) figure:
Screen resolution x fps = pixels/sec

Floating point operations per second (FLOPS) are increasingly becoming a critical parameter for mobile GPUs when it comes to graphics and compute performance. The FLOPS metric indicates the number crunching ability of a graphics processor and can be compared to the million instructions per second (MIPS) that a CPU can deliver.
This graphic shows the graphics performance evolution for mobile devices. As we can see, graphic performance evolution rate is simply amazing, as the PowerVR GX6650 to be used in the application processor integrated in smartphone sold in 2015 delivers 40 times the performance of the PowerVR SGX530 integrated for example in OMAP3 from TI, developed less than 10 years ago!

Raw GFLOPS results give you a precise evaluation of the “brutal” force of a Graphic device. Brutal because analyzing graphic performance without taking into account the power consumption or the power efficiency of a specific GPU, may provide some surprises and you may have to plug your smartphone for battery charging more frequently than expected. How to clarify this point? You should look at benchmark results about Long term performance:

Long term performance
If you are looking at a better indication of real-world workloads for current-generation graphics hardware, long term performance is probably your best bet. One of the benchmark to search for is: GFXBench 3.0 from Kishonti.

Do you remember this plot inserted as a comment in the blog “The TSMC iPhone6” from Dan Nenni? Now you get the complete picture, so you better understand why Apple is throttling A8 CPU after 10 minutes! That’s the only way to offer very good graphic performance at the beginning (to impress a potential buyer), and a decent power consumption on the long term.

You will find a lot more information about benchmarks and how to use it in this very interesting blog from Alexandru Voica (he is with Imagination Technologies, so the focus on PowerVR family!): “A consumer’s guide to graphic benchmark

From Eric Esteve from IPNEST

More Articles by Eric Esteve…..

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