Is GHz all that Matters in a CPU?

[NotAPCElitist]

What is the difference between a Core i7 5820K at 3.3 GHz and an Intel Pentium G3430 at 3.3 GHz? Isn't ghz all that matters or is there more to it?

 

[Heinzen]

The core clock (or GHz as you said), is just a rough measure of performance - obviously it determines how fast a CPU cycle happens, but that doesn't mean that 2 processors running at the same core clock will have the same performance. There are quite a few things that matters when talking about performance.

IPC (instructions per cycle) - which is literally what the name suggests, how many assembly instructions a CPU can perform in a clock cycle.

The cache memory (size & speed)

The bandwidth - your CPU has to exhange information with other components, the amount of data it can exchange at once - and how fast it can do that - is key to important tasks such as sending data to a memory block or read from a memory block. The bandwidth is the throughput ratio of data that the CPU can communicate with a different component - a memory controller for example.

Cores and Threads - essentially each thread can handle a different task. The more threads your CPU can handle at once, the 'faster' it can finish a certain task. Please note that multi-threading is highly dependant on how the software was coded, it's not entirely up to the processor.

_______________________

But to be quite honest, these aspects fall into the lower-level domain. For an end-user such as yourself, generally you want to see whether your tasks can make use of multi-threading (and if they can, how many threads your CPU can handle at 'once'), how fast each CPU core is and how big the Cache memory is.

 

[USAFRet]

What is the difference between a Core i7 5820K at 3.3 GHz and an Intel Pentium G3430 at 3.3 GHz? Isn't ghz all that matters or is there more to it?

Way more to it.
For instance...a Pentium 4 Prescott @ 3.8 GHz is VERY much slower than a current i5 @3.4 GHz.

 

[DonkeyOatie]

Depends on what you are doing with it. Like a car, is r.p.m. all that matters?

A CPU consists of cores (or Modules). A Pentium has two, the i7 you mentioned has six.
As a base, the Pentium core runs faster clock, However there are many other differences.

The 3430 is a bit older, so it is a bit less efficient (closing the gap a little) for each core
The 3430 has fewer and different resources available to it (closing the gap more and even reversing things) for each core.
The 5820K has Turbo Boost, so can increase speed on any core to 3.6Ghz for a while, to handle demanding tasks. The Pentium cannot.
The 5820K can be overclocked significantly and safely to at least 4.4Ghz per core.

At stock one core in a G3430 has similar performance to that of an i7 5820 both running light work at stock. Anyone wanting only to browse the internet would be foolish to get the i7.

However, when things get demanding

The 3430 can process two threads at full speed at once. It can handle more, but has to 'juggle them' more slowly.
The 5820K can process about 8.4 threads at full speed at once, with a combination of six cores and Hyperthreading that processes additional tasks during time that the cores are waiting for other things to do. The 5820K can handle more too and has to 'juggle' but it is a lot better at it than the Pentium.

A person whose main work was video editing, computation heavy graphics would be a fool to get the G 3430.

For modern gaming, more than two threads are needed, so again, the G3430 is lacking.

In this discussion we are considering two CPUs of very similar architectures and generations from the same manufacturer. When any of these things changes, architecture, generation, or manufacturer, the comparison becomes a lot more complex.

 

[photonboy]

In general, you can compare Passmark scores for:
1) Single core performance, and
2) TOTAL performance

For gaming, more than four true cores (not dual core with hyperthreading) we just look at the SINGLE CORE performance. For example:

https://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i5-3450+%40+3.10GHz&id=820
vs
https://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i5-4690K+%40+3.50GHz
vs
https://www.cpubenchmark.net/cpu.php?cpu=AMD+FX-4300+Quad-Core

Most games use at least TWO cores (not usually more than this fully though). Now, Starcraft 2 really only uses two cores and is often CPU bottlenecked at times (heavy battles) so frame rate is frequently roughly proportional to SINGLE CORE performance.

FX-4300 vs i5-4690K-> 1411 vs 2234

Roughly speaking it's possible to get 50% higher frame rates on an i5-4690K setup with the same GPU and settings.

Other stuff:
Some programs like HANDBRAKE can use eight or more cores/threads (but not necessarily during the entire rendering time) so total performance is more important. Thus an 8-core AMD with lower performance per core would do better than a fast Intel dual-core for Handbrake but again in Starcraft 2 and other games the dual-core Intel might win (since the games again might only use 2-3 cores well).

Hyperthreading:
This is when the same core is running a second task during the time it would otherwise be idle (getting new data to process). An i3-4170 is an example. It only has two physical cores, but each of the virtual cores is roughly speaking another core running at about 40%. The program must still be able to run enough threads to benefit.

Hyperthreading can even cause STUTTER issues in games if the main game thread gets assigned to run on the virtual core which has less processing power.

Summary:
So it gets confusing. Rather than repeat the first comment I thought I'd supplement it.

If you want a specific CPU then ask specific questions like "best build for $1000USD or whatever" as the CPU is just one component. It's all about the BALANCE of components.

 

[Davinlevey]

Here is a rough explanation of why the clock speed isn't the only factor: The frequency (Ghz) is how frequent the "clock" the processor is running at ticks in a second. 3.8 Gigahertz = 3,800,000,000 clock ticks per second. Each of those clock ticks the processor performs an action, and each processor technology handles those actions differently, some are more efficient than others. The for the most part the newer ones are better in this, and Intel does this better per core. Just because 24 hours go by doesn't mean you get the same amount of stuff done everyday.

I hope this helps out a bit!