GHz Degression

[CausticPuppy]

No it hasn't.
First. "Turbo" is pure marketing, CPUs never actually see those high speeds in the real-world since the OS spreads work across the CPUs, not just dumping everything onto one or two.

Second. The Pentium 4 hit 3.8GHz in 2004, over 7 years ago. So, no, GHz has not "generally gone up".

The OS cannot magically turn a single-threaded process into a multi-threaded one. Regardless, Turbo Boost also applies when 2 or 4 cores are active, not just a single core. The max turbo rate with multiple cores is lower than with a single core, but still higher than the base clock rate. With enough cooling, a quad core i7 might always run at the turbo frequency even when all 4 cores are used.

 

[goMac]

The OS cannot magically turn a single-threaded process into a multi-threaded one.

Eh. Not entirely true. The OS can multithread whatever APIs the app uses.

For example, it's entirely possible for the OS to swap out a single threaded QuickTime export API for a multithreaded one, and the app wouldn't even know, yet the app would become multithreaded.

 

[CausticPuppy]

Eh. Not entirely true. The OS can multithread whatever APIs the app uses.

For example, it's entirely possible for the OS to swap out a single threaded QuickTime export API for a multithreaded one, and the app wouldn't even know, yet the app would become multithreaded.

But switching a thread among cores is not the same thing as multithreading. And not every API call would have a multithreaded version.

At any given time, one core is doing that thread's work. As soon as you bring up the silent switch to a multithreaded API, well we're not talking about single-threaded any more, are we?

 

[goMac]

But switching a thread among cores is not the same thing as multithreading.

That's not what I said. Nowhere did I mention "switching a thread among cores."

And not every API call would have a multithreaded version.

No, not every API call is. But you said that an OS can't make an app multithreaded, and my point was that it certainly can.

At any given time, one core is doing that thread's work. As soon as you bring up the silent switch to a multithreaded API, well we're not talking about single-threaded any more, are we?

...which only proves my point?

Again, you said an OS can't make an app multithreaded. I was making a counter example. So yes, the OS throwing a "silent switch" can make an app not single threaded anymore.

Applications written in the last 15 years are built upon layers and layers of OS tools and APIs. If any of those become multithreaded, the app becomes multithreaded.