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Comment by Mobius01 | Hacker News Reader

I’m a layman, so I’d like someone from the community to elaborate on Sony’s approach of constant power to the CPU/GPU while the clocks are variable. My interpretation is that the silicon will downclock based on load - if it is only running the UI dashboard, it will slow down appropriately; if running an intensive software title, it will clock up to theoretical max frequency.

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They picked a fixed thermal budget based on realistic usage scenarios, and then translated that into a fixed power budget. They balance the power budget between CPU and GPU using SmartShift (https://www.amd.com/en/technologies/smartshift), which is their marketing name for the power management on the control plane of their fabric.

I have no idea if I understood it right, but what I interpreted was:

current systems throttle down when things start to overheat, this is "non-deterministic" and depends on environmental factors etc. this is harder for developers to optimise for

whereas the PS5 knows it's own power use and power budget, as long as it stays within that budget then it won't overheat. and this means the throttling is 'deterministic' - the same code running will always throttle in the same way at the same time, so this is easier for developers to test and optimise for

And easier for Sony to make a cooling system for.

How can this be true? If I put the PS5 within a small enclosed case with a poor ability to dissipate heat, it should overheat / throttle down thus making the throttling variable, no?

We're talking about running the hardware within its ambient spec. For example, PC turbo implementations might run faster at 10C than 20C ambient but the PS5 won't.

Apparently they have a really good cooling solution (which they haven't disclosed yet) so that even in a (almost) worst case scenario, developers can rely on the performance specs.

if true, this is kind of sad. would it be so hard to make a "dev mode" where the device pretends to be severely thermally throttled, target that performance for development, and then let everyone who isn't a complete idiot enjoy the full performance of the hardware?

That isn't what I took from it; it sounds like various components (the example given was CPU and GPU) can sort of "trade" energy budgets:

> send any unused power from the CPU to the GPU so it can squeeze out a few more pixels

What it sounded like to me (also a layman) is that they have a fixed energy budget that's tied to the thermal properties of a baseline unit in a neutral environment. As long as they're under that budget, they can boost up the clocks of individual components that are under load. So heavy-rendering cycles can use relatively more GPU and heavy-compute cycles can use relatively more CPU.

That might be totally wrong, though, and I would also appreciate an expert's explanation.

if it is only running the UI dashboard, it will slow down appropriately; if running an intensive software title, it will clock up to theoretical max frequency.

There should be power saving modes but that's not what they're talking about. Sony is saying that you can run the CPU at 3.5 GHz xor the GPU at 2.2 GHz but they can't both run at full speed at the same time. So maybe you can have CPU @ 3.3 and GPU @ 2.2 (favoring GPU) or you can have CPU @ 3.5 and GPU @ 2.0 (favoring CPU). I guess most games will favor the GPU but I'm not a game developer.

(As an aside, I coined the term "power shifting" in 2005 to refer to this concept and I'm happy to see it being incorporated into basically everything, even if they probably independently reinvented it.)

Surely it's the CPU at 3.5 GHz nand the GPU at 2.2 GHz

I’d like to understand what’s the benefit of this opposed to running at a fixed clock speed?

My guess is it has something to do with cost savings (cheaper to manufacture silicon that has to perform “better” some of the time as opposed to all of the time).

You can't do that with a console. All of them have to hit the min specs.

You can allow one game to use more gpu while reducing cpu and vise versa.

Just imagine a cpu heavy rts vs a graphic intense rpg

If they fixed the clock it would have to be lower which would lead to lower performance.

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