Core i5 or Core i7, which to buy?

For many consumers who are on the hunt for a new desktop or laptop PC, one of the biggest considerations is the type of processor. Two of the CPUs most often in contention are the Intel Core i5 and Intel Core i7. Discounting Core i3 (mainly found in budget systems) and AMD processors (another story entirely), the difference between Intel Core i5 and Core i7 can seem daunting, especially when the prices seem so close together once they're in completed systems. We break down the differences for you.

Price and Marketing
Simply put, Core i5-equipped systems will be less expensive than Core i7-equipped PCs. Intel has moved away from the star ratings it used with previous-generation Core processors in favor of a capability-driven marketing message. Essentially, the Core i7 processors have more capabilities than Core i5 CPUs. They will be better for multitasking, multimedia tasks, high-end gaming, and scientific work. Core i7 processors are certainly aimed at people who complain that their current system is "too slow." Spot-checking a system like the Dell XPS 13 Touch ultrabook, you'll find the Core i5 to be about $200 less expensive than a similarly equipped Core i7 system.

Core Confusion
For the most part, you'll get faster CPU performance from Core i7 than Core i5. The majority of Core i7 desktop CPUs are quad-core processors, but so are the majority of Core i5 desktop CPUs. This is not always the case, as there are dual-core mobile Core i7 processors and many dual-core mobile Core i5 CPUs. You might also see the rare six- or eight-core Core i7, but that's usually found with the desktop-only, top-of-the-line Extreme Edition models.

The Core nomenclature has been used for several generations of CPUs. Nehalem and Westmere use three-digit model names (i.e., Intel Core i7-920), while Sandy Bridge, Ivy Bridge, Haswell, and Broadwell CPUs use four-digit model names (such as the Intel Core i7-5500). Thankfully, unless you're shopping the used PC market, you'll find Ivy Bridge processors in closeout systems and budget PCs, while you'll find Haswell or Broadwell processors in most new PCs. Older-generation Nehalem, Westmere, and Sandy Bridge cores are found in older PCs and generally have lower performance. The essential takeaway is that to get better performance in each generation, buy a processor with a higher model number. For instance, an Intel Core i7-5500U generally has better performance than an Intel Core i5-5200U.

Give Me the Cache
In addition to generally faster base clock speeds, Core i7 processors have larger cache (on-board memory) to help the processor deal with repetitive tasks faster. If you're editing and calculating spreadsheets, your CPU shouldn't have to reload the framework where the numbers sit. This info will sit in the cache, so when you change a number, the calculations are almost instantaneous. Larger cache sizes help with multitasking as well, since background tasks will be ready for when you switch focus to another window. On currently available desktop processors, i5 CPUs have 3MB to 6MB of L3 cache, while i7 processors have 4MB to 8MB.

A Word on Turbo Boost
Turbo Boost is an overclocking feature that Intel built into its processors. Essentially, it allows the processor to run faster than its base clock speed when only one or two processor cores are needed (like when you're running a single-threaded task that you want done now). Both Core i5 and Core i7 processors use Turbo Boost, with Core i7 processors achieving higher clock speeds.

Hyper-Threading
Intel Hyper-Threading uses multithreading technology to make the operating system and applications think that a processor has more cores than it actually does. Hyper-Threading technology is used to increase performance on multithreaded tasks. The simplest multithreaded situation is a user running several programs simultaneously, but there are other activities that take advantage of Hyper-Threading, like multimedia operations (such as transcoding and rendering) and Web surfing (loading different elements, like Flash content and images, simultaneously).

The quick explanation is that all Core i7 CPUs use Hyper-Threading, so a six-core CPU can handle 12 streams, a four-core can handle eight streams, and a dual-core can handle four streams. Core i5 uses Hyper-Threading to make a dual-core CPU act like a four-core one, but if you have a Core i5 processor with four true cores, it won't have Hyper-Threading. For the time being, Core i5 tops out at handling four streams, using four real cores or two cores with Hyper-Threading.

Integrated Graphics
The Westmere generation of Core processors introduced Intel HD graphics, which are integrated graphics built into the CPU core itself. Previous Intel-integrated graphics were built onto the motherboard chipsets, rather than on the processor. You'll find DX10 Intel HD Graphics 2000/3000 in older Sandy Bridge processors, and new DX11-compatible Intel HD Graphics 2500/4000 in the third generation's Ivy Bridge processors. Newer Haswell fourth generation and Broadwell fifth generation processors have either updated Intel HD graphics (for example Intel HD Graphics 5000), or Intel Iris/Iris Pro options. Note that while high-end Intel processors will let you play 3D games at low quality settings, you will still need discrete GPUs from AMD or Nvidia to play 3D games at 1080p with ultra quality settings turned on.

The same numerical rules apply here, so Intel Iris Pro 5200 performs better than Intel HD Graphics 4600, which performs better than Intel HD Graphics 2500. You'll find Iris Pro and Intel HD 4600 on Core i7 CPUs, while Core i5 processors feature one of the myriad versions of Intel HD graphics, depending on the part number. Integrated graphics save power, since there's no extra graphics chip on your laptop or desktop's motherboard using power.

Long story short: Intel Core i5 is made for mainstream users who care about performance, and Intel Core i7 is made for enthusiasts and high-end users. If you follow this mantra, you're likely going to find the system you need.