Would a 2.5GHZ processor from a decade ago be the same speed as a processor now, at the same frequency?

Question

So would two processors running at 2.5GHZ (just a random frequency I’ve chosen) but one from 10 years ago and one from this year be equivalent in processor power. Does this measurement mean they are the same in raw power?

###### 2.5GHZ (Old Processor) = 2.5GHZ (New Processor)?

Or is it because of new architecture that the newer one is faster and in that case newer is always better due to more cores etc.

In that case doesn’t it make it confusing to use gigahertz to measure the speed of newer processor in comparison to previous generations?

Sorry for the long question, it’s just always bothered me and confused me on how to choose the best processor.

In: 5

Answer 1

The short answer is: no, as [this video shows](https://www.youtube.com/watch?v=8QOoQWvrQ-Y).

The longer answer, for those who don’t wanna watch: in your computer, there’s a tiny little clock. Every so often, it says “do something” – a clock cycle. Gigahertz is a measure of how often it is between the clock saying that – or, mathematically, how many times it says to do something in a second.

Now, on early CPUs, that “something” was exactly one “instruction” at most. Instructions are the building blocks of all code – stuff like “fetch this byte of memory” or “add these two numbers together”. Complete more instructions per second, and your CPU performs better.

Now, there’s two ways to accomplish that goal. The first way is to complete more cycles – increasing gigahertz. The second way, though, is to complete more than one instruction with every cycle. There’s several techniques to do this, but what’s important is that the instructions per cycle is not fixed.

A modern CPU will tend to have better IPC than an old one. Better IPC with the same cycles per second means more instructions per second – which is what actually matters.

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The reason we still use gigahertz is because it’s far, far easier to measure – and harder to manipulate. Let’s say one manufacturer’s CPUs perform really well in benchmark x, but less well in benchmark y – while the other manufacturer’s CPUs perform really well in y, but worse in x. Both manufacturers can say “we ran real benchmarks that show our CPU is 20% better than the competition at the same speed” – and conveniently ignore when they’re worse. The best route is to look at independent, reputable third party reviewers, because gigahertz – and all the other stats – isn’t a good indication of performance.