Intel Core i5 vs. Core i7: Which processor should you buy?

Whether you’re building your next PC or shopping for a new computer online, one of the questions that comes up from time to time is whether the Intel Core i5 or Core i7 is a better bargain. The short answer, “It depends,” isn’t all that helpful, so we’ve broken the data out in more detail and for both mobile and desktop processors. Here’s what you need to know.

Mobile Core i5 vs. Mobile Core i7

Because Intel has launched a reasonable set of SKUs for its 5th generation (Broadwell) hardware, we’ll use those chips for comparing the Core i7 vs. Core i5 stack. All of Intel’s mobile Core i5 processors are dual-core chips with Hyper-Threading, going right back to Sandy Bridge. What distinguishes modern 5th generation Core i5s is their TDPs — Intel offers Broadwell in 15W, 28W, and a single 47W SKU. That chip, the Core i5-5350H is also capable of addressing 32GB of RAM and offers Intel’s Iris Pro 6200 solution based on Crystal Well.

Intel’s Core i5 mobile lineup (Broadwell)

Here are the features that separate mobile Core i5 and Core i7 processors:
More cores: Many of Intel’s Core i7 processors are quad-core chips with Hyper-Threading enabled. This isn’t universal, however, and the company does offer five dual-core + Hyper-Threading SKUs.
Higher clocks: Intel’s dual-core mobile Core i7 chips typically have higher clock speeds than their Core i5 counterparts, even at the same TDP. The fastest dual-core Core i7 at 15W TDP is the Core i7-5600U, which runs at 2.6GHz base and 3.2GHz standard. The fastest Core i5 at 15W is the Core i5-5300U, which has a base clock of 2.3GHz and a max clock of 2.9GHz. The GPU on the Core i7-5600U is clocked 50MHz faster as well.
More cache: Core i7 chips carry either 6MB or 4MB of cache. Core i5 chips have 3MB, except for the Core i5-5350H, which has 4MB.
More addressable memory: Most of the Core i7 chips are limited to 16GB, like the Core i5, but there are four exceptions. The Core i7-5850HQ, 5950HQ, 5750HQ, and 5700HQ are all capable of addressing up to 32GB of RAM.
One important thing to note, however, is that how much performance you get out of a Core i5 vs. a Core i7 will depend a great deal on your laptop’s cooling solution and whether or not the chip can handle its own heat output. We’ve previously discussed how Intel gave OEMs more freedom to define their own TDP targets and skin temperatures, but this creates scenarios in which buying a faster Core M can actually result in worse performance as the chip hits its thermal trip point and down-throttles to keep cool.

Intel’s highest-end Iris Pro graphics are available in both Core i5 and Core i7 mobile SKUs

We can’t point to specific instances where this has tilted performance between Core i5 and Core i7 chips, but it’s likely to create at least a little “slosh” between the two core families. Generally speaking, if you truly want to emphasize low power, pick the CPU that has lower base and turbo clocks. Intel historically defined TDP as “The CPU’s average power consumption when running typical workloads over a period of time.” A chip with more headroom is a chip that’ll hit its throttle point faster.

Desktop Core i5 vs. Desktop Core i7

Because Intel has only launched a handful of Core i5 and i7 desktop parts, for now we’ll focus on the 4th generation cores (Haswell). One significant difference between the desktop and mobile markets is that all but one of Intel’s 23 Core i5 SKUs offer four cores, but no HyperThreading. Intel’s Core i5-4570T is the single exception to this — it’s a dual-core + HyperThreading chip. Another difference between the mobile lineup vs. the desktop cores is that the desktop versions of both the Core i5 and Core i7 officially top out at 32GB of addressable memory.
In fact, many of the differences we observed between mobile parts don’t apply to desktop hardware. The i7 family still carries more L3 cache (8MB, save for the Core i7-4770R, which has 6MB), as compared to the Core i5 family, which has 6MB of cache on every chip except for the Core i5-4570R, 4570 and 4670R, which have just 4MB. Clock speeds are a mixed bag — while the fastest Haswell Intel manufacturers is the Core i7-4790K at 4GHz base clock and 4.4GHz Turbo, the Core i5-4690K is clocked at 3.5GHz base and 3.9GHz Turbo — essentially equal to the Core i7-4770K.
Both the Core i3 and Core i5 families use Intel HD Graphics 4600 solution with the same 350MHz base clock and 1.2GHz maximum clock. Apart from Hyper-Threading and some small cache differences, the Core i5 and Core i7 are quite similar, with overlapping frequency ranges and feature sets. Support for Intel’s TSX-NI instructions is only available on one Core i5 SKU, but only two Core i7’s offer the capability.
Similarly, Intel only offers vPro on 13 of the 23 Core i5 SKUs, compared to 9 of the 12 Core i7 SKUs — but if you want vPro on a Core i5, you can get it.

What about performance?

To compare performance between the Core i5 and Core i7 families, I turned to Anandtech’s excellent CPU Bench database. While AT doesn’t have records on every chip released by Intel or AMD, they’ve got a very solid selection of comparable parts. I opted to check the Core i5-4690K vs. the Core i7-4770K. The 4770K has Hyper-Threading, a base frequency of 3.5GHz, can Turbo up to 3.9GHz, and has 8MB of L3 cache. The Core i5-4690K has the same clock speed but no HT and just 6MB of L3 cache. That’s about as perfect a match-up as you can ask for.
The graph below was generated by comparing Core i5 and Core i7 in each and every benchmark and taking the geometric mean of the results. This diminishes the impact of outliers (though in this case, the arithmetic and geometric means are quite close to each other). I’ve split the data into three sections — general compute, gaming performance with 1x GTX 770, and gaming performance with the GTX 770 in SLI.

Aggregate performance between the Core i5-4690K and Core i7-4770K. Data from Anandtech CPU bench

There are some differences in the data sets that we need to discuss. The aggregate General Purpose ratio doesn’t reflect the impact HT can have on various applications. There are a number of applications where HT makes no difference, a handful where it decreases performance (though never by more than 8 percent) and a several benchmarks that show gains of 10-30%. If we set a 3% threshold for a tying score, Hyper-Threading gives the Core i7 a win in 21 out of 36 tests. It ties the Core i5 in 14 tests, and loses to it outright in just a single benchmark (x264).
In workstation and consumer CPU workloads HT sometimes helps a lot, sometimes doesn’t help much at all, but almost never hurts.
Gaming, however, is a very different animal. In gaming, Hyper-Threading never offers a single performance boost, while it impacted BioShock Infinite’s minimum FPS by 11% (meaning the Core i5 outscored the i7). The net effect is a 2% performance decrease for Hyper-Threading.
In SLI gaming, we see a similar pattern, though this time it’s different games that take performance hits. The minimum frame rate for Sleeping Dogs was 10% faster on the Core i5 (56 vs. 61.8) and 5% faster in BF4 (86.4 vs. 82.9).
What this means, in aggregate, is that while Hyper-Threading probably doesn’t hurt gaming in most titles, you can’t depend on it to offer a significant performance boost, either.

What about AMD?

AMD isn’t a formal part of this article, but since I know people will ask, I took a look at how the FX-9590 compares against the Core i5-4690K. The news is not particularly good. There are a few well-threaded benchmarks where AMD can shine, including WinRAR, x265 encoding, multi-threaded Cinebench (both 11.5 and R15) and 7zip. The FX-9590 is utterly incapable of matching the 4690K’s single-threaded performance, which means AMD loses every test that can’t scale to eight cores or is single-threaded to start with.
The gap between AMD and Intel in game benchmarks is much smaller than in general CPU performance, and AMD’s FX-8350 and FX-9590 are capable of pushing perfectly acceptable frame rates, but the FX-9590 never outclasses the Core i5-4690K in any test. If you’re building a gaming box and you want to go AMD, you absolutely can — but pound for pound and watt for watt, the Core i5 wins this competition.

Which chip should you buy?

Right now, the Core i5 runs from $184 to $249 (oddly, the Core i5-4690K is actually cheaper than the Core i5-4670K, at $239). The Core i7 family, in contrast, clocks in at $304 to start with and goes up to $346.95. Again, the Core i7-4790K is better priced ($339) than the Core i7-4770K at $346.95. The Core i7-4790K is 1.39x more expensive than the Core i5-4690K, but the performance gains you see will be highly dependent on how you use the CPU. If you plan to do video editing, 3D rendering, Handbrake or do a lot of file decompression and compression, or you use specific programs that you know benefit from Hyper-Threading, then the more expensive Core i7 may be well worth the money. If you’re mostly looking to game, on the other hand, the Core i5 may be a better choice.
DirectX 12’s imminent release could offer the Core i7 a chance to prove itself, but DX12 games will trickle on to the market, not flood it. DirectX 11 and DX9 will remain important APIs for years to come, which means we have to wait and see which titles offer DX12 support and how it changes the Core i5 / Core i7 comparison.
It’s harder to make this call on mobile. Poor cooling will cripple any laptop and some of the boutique laptops on the market are sold with CPUs that they can’t possibly keep cool. I tend to favor the Core i5 over the Core i7 for mobile gaming because it helps preserve battery life and still offers good overall performance. CPU choice is just one element of a laptop — just be aware that higher-end CPUs may not deliver much of their expected performance if the chassis isn’t well designed for the chip it’s carrying.