The PS5 eschews years of traditional console design and goes for variable frequencies or boost clocks. However there is a huge misconception among people because of the word 'boost clocks'. To understand further, lets take a look at something that has boost clocks in the traditional sense - a PC processor (GPU or CPU, both will do). A PC processor usually has two clockspeed targets - a base clock (lower frequency) and a boost clock (higher frequency). Variable power will be supplied to the processor so that it consistently hits that base clock (so basically what the Series X is doing). However, if there is thermal headroom (i.e more power can be supplied to the chip without it overheating) the processor will be supplied with more power so that it hits the boost clock. However at this boost clock, the temperatures will start to rise and eventually the processor will have to come back to the base clock to prevent overheating. In this type of configuration, both the power and the frequency are variable.
The PS5's boost clock is not the same as this. Lots of people have been talking about how the teraflop number is a sham because the PS5 won't be able to run at this 'boost clock' most of the time. That is simply false and here's why:
The PS5 has a specific power limit i.e it's power consumption is not variable and is a consistent figure at all times. Thus the temperature that the chip outputs is the same at all times. This allows the designers to design a cooling system around the exact temperature that it outputs. What this means is that the PS5's fan is not gonna spin much faster or much slower depending on the how big or small power consumption is. Its going to spin based on ambient temps, as the thermal output of the processor is already know and they only need to account for the variance in ambient temps (which makes the temperature range that the cooling system has to be designed for much more predictable and exact i.e a one degree rise in ambient temperature can be more accurately accounted for than the rise in power consumption). So all the people who suffer through the obnoxiously loud and hot PS4s and PS4 Pros, rejoice for you have to suffer no longer (that is, if you're getting a PS5)!
How is Sony achieving this though? Well here is where the variable frequency part comes in. The PS5's processor will be able to see what the games are actually doing i.e what activity is going on in-game, and when those game scenarios occur where power consumption spikes up, it'll downclock. Game developers will be able to tell exactly when it is that this power consumption goes up and as such, be able to account for the reduced frequency then (so in a way, you have the predictability and reliability that comes with setting a specific frequency target, but it also mean that devs will have to work a bit harder to fine tune and optimise things). The crucial thing here is that it doesn't have to downclock by a lot. Remember when I said this a couple of paragraphs above:
Increase in power doesn't correspond to an equal increase in frequency i.e it does not scale linearly. To hit higher frequencies you need to input more and more amounts of power to the point where it becomes a case of diminishing results
Well the opposite is happening here. Decrease in Frequency leads to an exponential decrease in Power consumption. So a 2-3% decrease in frequency (that's about 40-70 MHz in the PS5's case) can deliver at least a 10% decrease in power consumption. So what this basically means is that the PS5 is going to be hitting the targeted clockspeed of 2.23 GHz most of the time (unlike a PC processor with boost clocks), when it downclocks it's not going to be by a significant amount (again, unlike a PC processor) and while doing all this it is going to remain cool and quiet. Quite an innovative and novel concept huh? This is why the PS5's variable frequency is unlike that of the boost clocks found on PC and shouldn't be compared.
