[SOLVED] Basic (newbie) question about overclocking

[JasonK3]

These days pretty much every CPU has a boost feature. I'm unclear on the specific goal of overclocking in a world where boost is ubiquitous. Here's my question. Does overclocking increase the BASE CPU speed, the MAX BOOST CPU speed, or does in increase the place in between the two where the CPU would usually run.

Here's an example to make my question more clear. Let's say you have a hypothetical CPU that has a base clock of 3.5Ghz and a max boost of 4.5GHz. Let's also say that it usually runs right around 4GHz when under heavy (multithreaded) workloads. Would overclocking:

A) Increase the base speed above 3.5GHz.
B) Increase the max speed above 4.5GHz
C) Increase where the Turbo Boost function usually makes the CPU run, in this case somewhere above 4Ghz.

If the answer is A then it SEEMS like you would need to raise the base speed above 4GHz to actually get any real-world gain since it turbos to 4GHz anyway.
If the answer is B then it SEEMS completely worthless because it would still only turbo up to about 4Ghz.
If the answer is C then it would clearly be useful, but I always here people say how much they overclocked their CPUs in terms of it's new speed (ie, overclocked to 4.7GHz) so it SEEMS like it's not C.

See why I'm confused? Clearly overclocking is extremely useful, but I don't understand how since I don't know how it actually affects CPU speed now that boost is a thing.

 

[Eximo]

Well, a lot of factors here.

Base clock can be ignored for the purposes of overclocking, though in your first idea you could raise the base clock that high, but that would just be akin to setting a fixed ratio.

Yes, you can increase the maximum boost speed with an overclock.

The key to remember is that base clock is all cores operating within a specified power/temperature range. And the boost clock is usually referring to a set number of cores. ie 4.5Ghz for 1 core, 4.4Ghz for 2 cores, etc. When you overclock you are typically using heavier duty cooling so that you can exceed these specifications. So you can run say, all cores at 4.7Ghz by increasing the voltage, and thus power, delivered and dissipated by the CPU.

 

[JasonK3]

Thanks Eximo. For my usage (which isn't gaming, it's productivity) I almost exclusively care about fully multi-threaded workloads where every core is under full load. I'm also not looking to go too overboard with the cooling. I was considering a mild overclock on my next system, but it sounds like overclocking doesn't make a lot of sense for my particular use case.

 

[hftvhftv]

Thanks Eximo. For my usage (which isn't gaming, it's productivity) I almost exclusively care about fully multi-threaded workloads where every core is under full load. I'm also not looking to go too overboard with the cooling. I was considering a mild overclock on my next system, but it sounds like overclocking doesn't make a lot of sense for my particular use case.

Overclocking is for enthusiasts that don't need 100% stability and are able to replace failed parts due to overstressing. If you're use is productivity overclocking is just going to make your system run louder, hotter, and less stable, even if it is overclocked properly.

 

[Eximo]

I would say there are many professionals who will still overclock if the time/money equation is right. The key there is to find a maximum performance point that is 100% stable, which is why you hear about people doing 24h prime95 runs and the like. I don't usually take it that far.

I run my CPU at 5Ghz (4.5Ghz stock), but I don't do anything particularly professional with it. Pretty sure AVX loads would destroy it though. I tested my last CPU under AVX just to be sure and went with a more conservative overclock of 4.3Ghz up from 3.9Ghz stock (i7-4770k)

The part about noise/temperature is true. Even with a de-lid and re-paste and custom water cooling my CPU still regularly hits the low 80s.