Cerny: Devs Don’t Have to Optimize in Any Way for PS5’s Variable Clocks, It’s All Automatic
Following Mark Cerny's highly technical PS5 deep dive, a great number of questions remained, particularly after the PlayStation 5 system architect revealed how the next-generation console from Sony featured variable clocks based on AMD's SmartShift technology for laptops.
Game developers have been used to optimize their games for fixed clocks, which led many (including Digital Foundry's John Linneman) to imagine this would most likely be a problem.
However, in a follow-up interview with Digital Foundry published on Eurogamer two days ago, Cerny clarified the PS5 won't have any such problem as it will be all handled automatically by the system.
Developers don't need to optimise in any way; if necessary, the frequency will adjust to whatever actions the CPU and GPU are performing. I think you're asking what happens if there is a piece of code intentionally written so that every transistor (or the maximum number of transistors possible) in the CPU and GPU flip on every cycle. That's a pretty abstract question, games aren't anywhere near that amount of power consumption. In fact, if such a piece of code were to run on existing consoles, the power consumption would be well out of the intended operating range and it's even possible that the console would go into thermal shutdown. PS5 would handle such an unrealistic piece of code more gracefully.
That said, the PS5 system architect confirmed the console devkit's support for fixed clocks as that can be helpful during game development. Still, he added that all PlayStation 5 titles will be exploiting the SmartShift-based technology upon release in order to maximize power.
Regarding locked profiles, we support those on our dev kits, it can be helpful not to have variable clocks when optimising. Released PS5 games always get boosted frequencies so that they can take advantage of the additional power.
How did Sony manage to get such high 'boost clocks' on the GPU, anyway? Even our own Usman from the hardware team was skeptical on how the PS5 could maintain a peak 2.23GHz GPU frequency often enough. Cerny did mention finding a 'hotspot' of frequencies as one of the breakthroughs in the console's design phase.
One of our breakthroughs was finding a set of frequencies where the hotspot - meaning the thermal density of the CPU and the GPU - is the same. And that's what we've done. They're equivalently easy to cool or difficult to cool - whatever you want to call it.
Will AMD employ the SmartShift technology on their RDNA 2 graphics cards for desktop PC as well? It won't be long before we find out, as the latest rumors suggest AMD's RX Navi 2X to be scheduled for an October launch.