What is CPU/GPU Boost Clock?

[AstroBenny]

Hi, I am a little confused about what a boost clock is on the cpu/gpu.

I assume the base clock is what the gpu/cpu runs at when it is not being pushed and they always run at this base clock but never below it?

And the boost clock is what the cpu/gpu can go to when it is under load? But then for example if the cpu has a base of 3.5ghz and turbo's up to the boost of 3.9ghz why not just call it a 3.9ghz processor and let it automatically decide the required clock?

Also, when you are overclocking, are you increasing the base clock or the boost clock, or neither

I'm confused..

 

[Sakkura]

It may not be able to sustain the max boost clock indefinitely, so it's only there for short bursts of activity. Particularly for CPUs, where the top turbo boost speed is only available when a single core is under load, and the rest are inactive. The extra available power and cooling is used to allow that single core to run extra fast, to more quickly finish tasks that can only run on a single core.

 

By the way, at very low load they can idle at clocks below the base clock. Like a graphics card idling at 350 MHz or a CPU at 800 MHz. Saves power.

[Lord_Karango17]

I agree with just having the boost clocks of gpu's be the base clock, as unless you are manually overclocking, or it is factory overclocked, the boost clock of a gpu does not change, however there is a little more to it on the cpu side.

 

That 3.9 ghz may indicate the single threaded boost clock, that it will maintain if only one of the cores is under load, as it can afford to push it further. In a 4 core load however, like synthetic benchmarks, or rendering, it wont be able to reach those clocks/ is not validated for those clocks (it might get too hot on the stock cooler at those speeds).

 

Both the gpu, and the cpu will however clock down when they are not needed (my gpu runs at around 300mhz when it is not used, and jumps up to 1270mhz when it is under load, and it is a similar story for the cpu)

[Samfisher]

Base clock is the minimum frequency it will run if below a temp threshold.  Boost is when you are below the temp threshold and the CPU/GPU decides it can ramp up the speed while keeping under the temp threshold/voltage threshold.  Boost clocks for CPU typically only mean 1 core at that speed while the rest is at base clock or less, depending on what workloads you are throwing at it.

When you OC, you disable Boost either way, cos you set the same frequency for all cores and find a voltage sweet spot for it and maintain it at that speed.