PlayStation 5 Has Enough Power To “Potentially” Run Both CPU and GPU at Their Limits; Games Will Always Get Boosted Frequencies
One of the most interesting features of the upcoming PlayStation 5 console is the boost clock feature. Today, lead system architect Mark Cerny talked more about how this will work.
In a recent talk with Digital Foundry, Mark Cerny confirmed that the PlayStation 5 boost will not use the actual temperature of the die, but an algorithm in which the frequency depends on CPU and GPU activity. Using any other criteria would make consoles have highly inconsistent behaviors.
We don't use the actual temperature of the die, as that would cause two types of variance between PS5s. One is variance caused by differences in ambient temperature; the console could be in a hotter or cooler location in the room. The other is variance caused by the individual custom chip in the console, some chips run hotter and some chips run cooler. So instead of using the temperature of the die, we use an algorithm in which the frequency depends on CPU and GPU activity information. That keeps behavior between PS5s consistent.
If you play the same game and go to the same location in the game, it doesn't matter which custom chip you have and what its transistors are like. It doesn't matter if you put it in your stereo cabinet or your refrigerator, your PS5 will get the same frequencies for CPU and GPU as any other PS5.
Mark Cerny also addressed how boosting will work. The team made sure that the PlayStation 5 is very responsive to power consumed so that boosting will take a very short time, and with no noticeable lag.
There isn't a lag where extra performance is available for several seconds or several minutes and then the system gets throttled; that isn't the world that developers want to live in - we make sure that the PS5 is very responsive to power consumed. In addition to that the developers have feedback on exactly how much power is being used by the CPU and GPU.
One of the biggest questions regarding boosting was if the PlayStation 5 is capable of running both the CPU and GPU at their limits. Many speculated that this wouldn't be possible, but it seems like developers won't be forced to make a choice, as the console will be "potentially" capable of running both the CPU and the GPU at their limits of 3.5GHz and 2.23GHz
The CPU and GPU each have a power budget, of course the GPU power budget is the larger of the two. If the CPU doesn't use its power budget - for example, if it is capped at 3.5GHz - then the unused portion of the budget goes to the GPU. That's what AMD calls SmartShift. There's enough power that both CPU and GPU can potentially run at their limits of 3.5GHz and 2.23GHz, it isn't the case that the developer has to choose to run one of them slower.
How boost will influence game design remains to be seen, but it seems like all games will always get boosted frequencies. Mark Cerny did confirm that the PlayStation 5 devkits featured locked profiles to help developers optimize their games, but these performance profiles will not be found in the actual console so that all games will always be able to take advantage of the additional 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.
The PlayStation 5 console will be released later this year worldwide.