What's the difference between an Intel Core i3, i5 and i7?

We take a look at Intel's Haswell family of chips

At this point, children born in the year Intel debuted their first Core processor are almost old enough to drink.

Over a half-dozen generations of Intel Core i3, Core i5, and Core i7 CPUs have come and gone since then but many buyers are still asking the same questions. And unless you’re the kind of person looking to embrace AMD’s new Ryzen processors (Looking to learn which CPU is best: Intel Core i7 or AMD Ryzen? Check out our full feature here), you’re gonna have to make a choice between the three. 

In the past, we’re analysed what the difference between an Intel Core i3, i5 and i7 CPU was for things like Intel's 7th gen. Kaby Lake processors and whether Google’s mesh node Wi-Fi system lives up to the hype. But with the advent of Intel’s new Comet Lake, Canon Lake and Ice Lake CPUs, there’s a whole new generation of PC buyers looking to ask themselves the same familiar questions.

Thinking of building a new PC around Intel’s high-end Core i9 processors? Check out our guide to Which Intel Core CPU is best here

No matter who you are, you’ll want to know whether an Intel Core i3, i5 or i7 CPU is the right choice for you and we’re here to help. 

Core i3, Core i5, Core i7 — the difference in a nutshell

If you want to boil things down to something plain and simple, then generally speaking, most Core i7s are better than most Core i5s which are in turn better than most Core i3s. 

Below that, you’ve got fare like the Intel Celeron and Intel Pentium processors. We’re not going to go into those, since this article is focused on the difference between Intel’s Core i3, Core i5 and i7 CPUs, but they do merit a mention.  

intel-core-i9-logo-100791578-orig.jpgCredit: Intel

Regardless, the main thing you need to keep in mind here is that the 3, 5 and 7 attached to each family of Intel Core processors are simply meant to be indicative of their relative processing power. They’ve got nothing to do with the number of cores in each CPU nor the speed of each. Intel’s Core i7 CPUs don’t have seven cores nor do Core i3 have three cores.

Which family an Intel Core CPU falls into is based on a collection of criteria involving their number of cores, clock speed (in GHz) and cache size. The number of Intel technologies they integrate also plays a role. In other words, you’re much less likely to find things like Turbo Boost and Hyper-Threading in an i3 processor compared to an i5 or i7 processor. 

At their most basic level, these numbers reflect where each class of Intel Core CPU sit relative to one another and are intended to give consumers an idea of the kind of performance they should expect from each. 

Essentially, the idea here is that:

  • An Intel Core i3 provides adequate performance for basic tasks

  • An Intel Core i5 provides good performance for most tasks

  • An Intel Core i7 provides great performance for even the most demanding of tasks

Since some older i7 CPUs might not out-perform more recent i5 CPUs, these designations shouldn’t always be taken as gospel but if you’re after a short and easy way to understand which processor is better, the numbers attached to each Intel Core family will do exactly that.

Of course, Intel’s Core i3, i5 and i7 processors can also be grouped in terms of their target devices. Some are intended for us inside laptops, others are intended for use with desktop PCs. 

In some cases, the difference in specs and performance for the desktop and laptop variants of Intel’s i5 and i7 CPUs can be quite significant. However, to avoid confusion, this article is going to be focused on the desktop variants. 

Number of cores

intel-xmm-8160-modem-1-100779874-orig.jpgCredit: Intel

While the number of cores inside an Intel Core CPU isn’t everything, the more cores there are, the more tasks (known as threads) can be served at the same time. This means that a PC with a higher core-count is going to be better for tasks where multithreading is important, such as web servers, web browsers and select video games.

And while there isn’t a hard and fast rule around it, you’re more likely to find less cores in a Core i3 than you are a Core i5 or i7. With a few exceptions, such as Intel’s 8th Gen Core i3 “Coffee Lake” CPUs, most Core i3 CPUs only have two cores. 

The reason for this is that i3 processors are designed to hit a lower price-point. They tend to be found inside PCs that target a more budget-conscious market-segment where the demand for a device to be affordable is greater than the demand for higher performance. 

As you’d expect, Intel’s Core i5 processors tend to be more powerful. Part of this comes down to faster average clock speeds. Part of this comes down to additional cores. 

In previous year’s Intel’s Core i5 CPU line-up has generally featured four cores. However, in more recent iterations like the 9th-Gen Coffee Lake refresh, Intel have upped the ante to six cores for many of their i5 CPUs. This includes stuff like the Intel Core i5-9400, Intel Core i5-9500 and Intel Core i5-9600

Lastly,  you’ve got Intel’s Core i7 CPUs. Again, you’re looking at both faster average clock speeds and additional cores. Intel’s Kaby Lake i7 Core CPUs included only four cores but the more modern Coffee Lake family of i7 CPUs feature up to eight cores and standard clock speeds that range go up to 3.6Ghz. 

At this point, you may be wondering just how important clock speeds are. The answer: pretty important. However, when it comes to clock speed, there are a few things you’ll want to keep in mind. 

The first is that, in general, a higher clock speed is better. Now, due to the thermal issues involved, processors with more cores tend to operate at a lower clock speed. 

This brings us to the second thing you’ll want to keep in mind.

Although a faster core is better than a slower one, it might not necessarily be better for the tasks you want to use your computer to do. Many applications only run single-threads while others are designed to utilize multiple. For cases where the latter applies, such as video rendering and gaming, having more cores is going to offer up an enormous improvement over having faster ones. 

For more everyday things like web browsing, an i5 processor with a higher clock speed is probably going to offer more bang for your buck than a beefier i7 might. Still, sometimes it’s more important to have those extra cores than an i5 or i7 CPU includes and often-times the choice between one Intel Core CPU and another will come down to whether you want to have a CPU with more cores or one with better clock speeds. 

The other thing you’ll want to factor in here is that there’s an important difference between a CPUs standard clock speed and turbo clock speed. The former is the normal clock speed that an Intel CPU is able to deliver. The latter refers to the fastest speeds it can reach using Intel’s Turbo Boost features.

These sorts of technologies, found exclusively in Intel CPUs, are one of the key things that separate i3, i5 and i7 processors - since the more-affordable i3 CPU (plus some i5 CPUs) often don’t include them. 

Find out more about Intel Turbo Boost, Cache size, Hyper-Threading on the next page.

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David Parkinson

PC World
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