Clock speed importance

[macman4789]

Hi,

With the many discussions about clock speed and thermal throttling I wondered whether someone could answer a question that my not so knowledgeable self could not.

Is clock speed like for like. So for example in single core usage would the 2.4 i5 in the MacBook Pro 13” be quicker in single core usage than say the 2.3 i9 15” MBP because it’s base clock speed is lower?

I know that when we move into multi core it becomes a non question as the i9 has 8 cores, but would any processor with a higher base clock speed keep up with the i9 if it’s got a higher clock speed than the 2.3 i9? I’m sorry if it’s an easy question to answer but I don’t know and would like to understand it more.

Thanks

 

[Super Spartan]

Depends on the app. If an app is only using a single core, then as the old saying says "Clock speed is king" so a higher clock speed on a single core would still be better than slightly lower speed with multi-cores.

 

[smbu2000]

You mention single core usage, but if both CPUs were only using one core then they would be turboing up and would most likely reach their max turbo speed. Using more cores slows down the max clockspeed that each CPU can achieve.

The i5-8279U in the 13” can turbo up to 4.1GHz. The i9-9880H in the 15” can turbo up to 4.8GHz. So the i9 would still win as it can clock higher.

 

[leman]

Is clock speed like for like. So for example in single core usage would the 2.4 i5 in the MacBook Pro 13” be quicker in single core usage than say the 2.3 i9 15” MBP because it’s base clock speed is lower?

No. Clock speed on modern CPUs is dynamic — it changes based on circumstances. The base clock listed is the clock that the CPU is expected to run when executing a demanding multi-threaded workload. E.g. a 2.4 i5 in the 13" is expected to run at or above 2.4Ghz for prolonged periods of time if you load up all the 4 cores with work.

If you execute a singe-threaded workflow though, other cores can clock down or even be turned off, which allows the one or two cores you are actually using to run much faster. So here is where you need to look at turbo clock limits. As pointed out by smbu2000, the i9 has much higher turbo clocks, so it will will in both single-threaded and multi-threaded workflow.