There is a wealth of difference between Intel Core I5 vs Core i7 CPUs. We break it down and explain what it all means for your next desktop or laptop purchase.
For many consumers shopping around for a new desktop or laptop PC, one of the biggest considerations is the type of processor, and the two most often in contention are the Intel Core i5 and Core i7. Discounting Core i3 (mainly found in budget systems) and AMD processors (another article 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 systems. 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 i3 and Core i5 CPUs. Core i7 will be better for multi-tasking, 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 midrange Dell XPS 8500 desktop, you'll find the Core i5 about $150 less expensive than a similarly equipped Core i7 system.
For the most part, you'll get faster CPU performance from Core i7 parts than Core i5. The majority of desktop Core i7 CPUs are quad-core processors, while many mobile Core i5 processors are dual-core. This is not always the case, as there are mobile dual-core Core i7 processors, and likewise several desktop quad-core Core i5 processors. Then of course you'll see the rare six-core Core i7, which are usually found with the desktop-only Extreme Edition top-of-the-line models.
The Core nomenclature has been used for several generations of CPUs. Nehalem and Westmere use three-digit model names (i.e. Core i7-920), while Sandy Bridge and Ivy Bridge CPUs use four-digit model names (Core i7-2600). Thankfully, unless you're shopping the used PC market, you'll find Sandy Bridge processors in closeout systems and budget PCs while you'll find Ivy Bridge processors in most new PCs. The essential takeaway is that to get better performance in each generation, buy a processor with a higher model number (e.g., a Core i7-3770 generally has better performance than a Core i5-3450).
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 the numbers sit in. This info will sit in the cache so that 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 8MB to 15MB.
A Word on Turbo Boost
Turbo Boost refers to Intel's "overclocking" feature 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, of course.
Intel Hyper-Threading uses multi-threading technology to make a processor appear to have more cores than it physically has to the operating system and applications. Hyper-Threading technology is used to increase performance at multi-threaded tasks. The simplest multi-threaded situation is a multi-tasking user running several programs simultaneously, but there are other tasks that take advantage of Hyper-Threading like multimedia operations (like transcoding, rendering, etc.) 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 handles eight streams, and a dual-core handles 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 4 streams, using four real cores or two cores with Hyper-Threading.
The Westmere generation of Core processors introduced Intel HD graphics, integrated graphics built into the processor 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 currently shipping Sandy Bridge processors, and new DX11-compatible Intel HD Graphics 2500/4000 in the newer Ivy Bridge processors. Same numerical rules apply, so Intel HD Graphics 4000 performs better than Intel HD Graphics 2000. You'll find 3000 and 4000 on Core i7, while Core i5 features one of all four versions of Intel HD graphics, depending on the part number. Integrated graphics saves power, since there won't be an extra graphics chip on your laptop or desktop's motherboard using power.
So, long story short: Core i5 is made for mainstream users who care about performance, and Core i7 is made for enthusiasts and high-end users. If you follow this mantra, you're likely going to find the system you're looking for.