I spent much of my teenage years sat in front of a monitor with a keyboard and mouse blasting away friends on the other side of the town in a bit of first person shooter action. The rest of the time I would be thinking about what graphics card I would need to run the same game at a slightly higher resolution or with more effects enabled. If I had two cards, would that double the frame rate giving me some kind of edge on my friends? The arms race in discreet graphics cards was always about delivering the ultimate performance no matter the cost – and ultimately the only cost was that on the consumer’s wallet.
Coming back to today’s world, a significant amount of gaming played on mobile devices. In the mobile GPU space, it’s very easy to be drawn into a similar battle for ultimate performance when comparing GPUs. But here there is one cost that is critical: power or, more specifically, thermal limits. The GPU will always keep giving performance, but if you cannot sustain that performance due to the thermal constraints of a mobile platform, there is little point in having that performance available. Not only that, but you would also want to use your phone to make a call, chat with friends, check e-mails etc, after a few hours of heavy gaming without having to worry about your battery running low.
When ARM talks about graphics performance, we specifically use the term energy efficiency, or delivering the maximum performance within this constrained thermal budget. It’s worth pointing out at this point that the “constrained” thermal budget never increases (~2.5W for total SoC power in a high-end smartphone that also needs to include other components such as CPU, memory etc) so the only way we can keep up with the curve in terms of performance requirements for the latest content is to keep the Mali GPU architecture constantly evolving with new innovative technologies and optimizations.
Looking at the latest high-end GPU from ARM, the ARM® Mali™-T860, we improved energy efficiency by 45% compared to the Mali-T628 across a wide range of content. That means it is able to deliver 45% more performance within the same thermal budget. The comparison is core for core in the same process node. In reality, as the industry moves forward with process nodes, we see even greater improvements in energy efficiency in end devices.
From generation to generation the Mali Midgard GPU family has made step improvements in energy efficiency. These have come both from innovative bandwidth reduction technologies such as AFBC (ARM Frame Buffer Compression) or Transaction Elimination (Jakub Lamik's recent blog titled Should Have Gone to Bandwidth Savers covers these technologies and more in extensive detail) and micro architectural optimizations designed around the content we run every day.
Looking at the Mali-T860 GPU we recently launched. ARM focused on real life use cases such as high-end gaming, casual gaming and the user interface for its hardware improvements. Optimizations like quad-prioritization result in significant efficiency improvements for casual gaming and user interface. Given that users spend a large proportion of time playing these types of games or navigating between applications on a device, we feel it is extremely important to focus on such use cases and ensure we are able to handle them in an energy efficient way. Ultimately, the user gets a smoother experience for longer.
Another optimization introduced in the Mali-T760 and enhanced in the Mali-T860 is Forward Pixel Kill. This feature reduces the amount of redundant processing the Mali GPU has to do when pixels are occluded. This is especially effective in applications that use inefficient draw ordering.
In summary, when comparing GPUs in our industry, performance alone is not a useful metric when energy efficiency is not included in the mix. Mali GPUs have been designed from the ground up to be extremely energy efficient not only within the GPU itself but also from a system wide perspective. We will continue to innovate in this area for each new generation of Mali GPU products.