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

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

Intel Turbo Boost Explained

Intel’s Turbo Boost feature allows a processor to dynamically increase its clock speed whenever the need arises. The maximum amount that Turbo Boost can raise clock speed at any given time is dependent on a number of factors. This includes the number of active cores, the estimated current consumption, the estimated power consumption and the overall processor temperature.

Using the Core i5-4570T as an example, its maximum allowable processor frequency is 3.6GHz while its base clock speed is 2.9Ghz. An 4th-Gen Haswell i3 CPU like the Core i3-4330 has a higher base clock speed of 3.1Ghz. 

Fortunately, since none of Intel’s Haswell Core i3 CPUs have Turbo Boost, the i5-4570T can outrun them whenever it needs to. 

Because all of Intel’s Core i5 and i7 processors are equipped with the latest version of this technology — Turbo Boost Max Technology 3.0  — all of them can outrun any Core i3.

Cache size

The Intel Inside marketing campaign began in 1991. Intel initially spent $250 million on the campaign, which targeted consumers rather than industry insiders.
The Intel Inside marketing campaign began in 1991. Intel initially spent $250 million on the campaign, which targeted consumers rather than industry insiders.

Another thing that sets Intel’s i3, i5 and i7 apart is cache size.  

Both your computer’s RAM and its CPU cache serve as holding areas for frequently used data. Without them, the CPU would have to keep on reading from the hard disk drive, which would slow everything down and make even simple tasks take a lot longer.

See, whenever a CPU finds that it keeps on using the same data over and over, it stores that data in its cache. A CPU’s Cache is just like RAM, only faster — since it’s built into the CPU itself.    

Basically, RAM minimises interaction with the hard disk, while cache minimises interaction with the RAM. As you might be able to guess, this means that a CPU with a larger cache allows for more data to be accessed faster. 

This is one major reason why an i7 outperforms an i5 — and why an i5 outperforms an i3.

What's more, CPU cache sizes have grown significantly in recent years. 

Intel’s 4th Gen Haswell Core i3 processors had either 3MB or 4MB of cache, Haswell Core i5s had either 4MB or 6MB of cache and Haswell Core i7 CPUs had a hefty 8MB of cache, except for the i7-4770R, which had only 6MB. 

In contrast, Intel’s more modern 8th-gen Coffee Lake i3 CPU feature either 6MB or 8MB. Meanwhile, 8th-Gen Coffee Lake i5 and i7 CPUs boast double their fourth-gen counterparts at 12MB and 16MB, respectively. 

Hyper-Threading

Although the analogy isn’t perfect, Hyper-Threading is basically the equivalent of something like turbo-boost when it comes to increasing the power of your CPU’s cores. 

In normal circumstances, only one thread can be served by one CPU core at a time. If a CPU is a dual-core, then supposedly only two threads can be served simultaneously. If your CPU has four cores, it can handle four threads at once. If your CPU has six cores….you get the idea.

Hyper-Threading changes this dynamic in a pretty significant way because it allows a single core to serve multiple threads at once. 

For instance, a dual-core Core i3 with hyper-threading can serve two threads per core rather than the regular one per core. In other words, a total of four threads can run simultaneously and a quad-core Core i5 processor that doesn’t support Hyper-Threading is going to be about as capable as a dual-core Core i3 processor that does -at least when it comes to the number of threads it can handle at once.

This is one of the many reasons why Core i7 processors are the considered the creme de la creme when it comes to mainstream desktop processors. Not only do they boast the most cores, they also support Hyper-Threading and are capable of much higher thread-counters. 

Essentially, where i5 CPUs offer you great core-counts and clock speeds plus some of the best performance-enhancing technologies Intel have at their disposal, Intel’s i7 CPUs offer you almost every bell and whistle the company have at their disposal. 

Intel’s Core i9 CPUs push this even further, by increasing the core-count to double digits. Intel’s latest i9 CPUs go as high as 18-cores and 36-threads. For more on Intel’s high-end Core i9 processors? Check out our guide to which Intel Core CPU is best here

Intel Core i3 vs Intel Core i5 vs Intel Core i7

If you’re the kind of person who wants to buy or build a computer that’ll last, you have to ask yourself what you’re going to use it for. 

If you do a lot of things at the same time on your PC, then it might be worth forking out the extra cash for an i5 or i7. Gamers in particular will want to opt for the latter, as it’s always better to sit closer to the recommended system requirements than its minimum system requirements.However, if you only use your PC to check emails, do some banking, read the news, and download a bit of music, you’re probably going to be OK with the cheaper i3.

The other deciding factor here should be whether or not the things you’re doing on your next PC are going to be things that can actually make use of technologies like Hyper-Threading. In other words, you need to look into and learn whether the applications and programs you use have any sort of multithread capability. 

Many modern photo editors and video editing programs are multi-threaded, for example. However, there are no guarantees and taking the time to Google it for yourself could potentially save you money. 

Hopefully this article has given you some insight for your next CPU selection and you now have a better idea of what the differences between Intel’s Core i3, Core i5 and Core i7 CPUs are. 

If you’re still a little confused about things like threads and cores or want to learn more about Intel’s ultra-powerful i9 CPUs, be sure to read our guide to which Intel Core CPU is best here.  

Either way, happy computing!

This article was originally written by David Parkinson and then updated by Fergus Halliday in 2019. 

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David Parkinson

PC World
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