In November 2008, Intel changed how it branded its computer processors (CPUs). Instead of naming each processor after how fast it was or how many cores it had, Intel named each processor after how high-performance it was at the time it was released.

The Core i3 brand included low-end processors, like the older Core Duo or Celeron processors. The Core i7 processors were the high-end processors, taking over from the Pentiums. In between Core i3 and Core i7 are the Core i5s—a mid-range line that has most often been made up of older Core i7 processors.

Let’s look at each of these processors in detail, and see how their laptop variants work.

Intel Core i3 Laptop CPUs

Most laptops use processors specifically designed for laptops. These processors tend to be more power efficient than desktop processors and also include better “speed stepping” technology which allows the processor to slow down when the computer isn’t busy, saving even more power. All Core i3 models designed for mobile include an “M” in their model name. For example: Core i3-4010M.

All Core i3 mobile processors released so far have only had two cores. So far, this has been the major difference from the Core i5 and Core i7 processors, which often have four cores.

A Core i3 processor was considered low-end when it was introduced, so if you’re buying a new laptop, you’ll get a processor that’s fast enough to run most business applications, surf the web, and do other normal activities.

If you’re buying a used laptop with a Core i3, remember that the processor will not be as fast as current Core i3 models, although (as of this writing) most Core i3s are still in the same basic performance range. For example, the Core i3-330M released in January 2010 has two cores running at 2.13 gigahertz (GHz) compared to the Core i3-4110M released in April 2014 with two cores running at 2.60 GHz. (The later model also has some other processor enhancements, but nothing too significant.)

To determine the full performance characteristics of any processor, you’ll simply have to search the web for its processor name. However, in general, you can depend on the Core i3 processors to deliver reasonable performance at excellent prices.

Intel Core i5 Laptop CPUs

Most Core i5 processors are just older Core i7 processors, or current Core i7 processes with fewer cores. Like the Core i3 mobile processors, many i5 processors only have two cores. Although this reduces performance, it also saves power and reduces heat—an important consideration when your laptop might be resting on your legs.

Some Core i5 processors do include four cores. None so far have included six cores. A few laptops with Core i5 processors (and more laptops with Core i7 processors) might have dual processors—that means a laptop with dual i5 four-core processors will actually have eight cores available for use. That’s a fast laptop.

Recent versions of the Core i5 series have introduced additional special-purpose mobile processors, such as the “U” series for Ultra-low power netbooks. If you’re considering a laptop-like device with a processor that doesn’t include the letter “M”, I suggest you compare its specifications against a model “M” processor with the most similar model number. For example, compare Core i5-3317U against Core i5-3210M. Lower power processors will typically trade a bit of speed for extra power savings.

Unless you’re pinched for cash, the Intel Core i5 series is where most people want to buy. These processors are fast enough to run almost all modern games and high-performance applications, but affordable enough that you won’t regret the purchase.

Intel Core i7 Laptop CPUs

For the high end of its processor line, Intel decided to go all-out. Having four cores in an Core i7 mobile processor is the rule, not the exception, and you will very often find dual-processor laptops. If you have lots of money, you may even find a laptop with 4 processors with 4 cores each—giving you 16 cores for maximal speed.

However, even if you don’t go core-crazy, you’ll find that Core i7 processors offer the best performance for gaming and for processing-heavy business work. Software developers who have to frequently recompile code love them.

Because they’re primarily purchased by high-end users who continually upgrade to the latest high-end technology, you can often get a good deal on used laptops with Core i7 processors, saving 25% to 50% of the sticker price on a laptop that’s only a year or two old.

However, be careful: there are more Core i7 processor types than Core i3 and Core i5 combined, so making comparisons between different models is difficult. If you recall the comparison between Core i3 models earlier, you saw that the newer models were only a little faster than the older models. That’s not true with the Core i7’s: this year’s model, the Core i7-4940MX, has four cores at 3.10 GHz compared to 2010’s model, the Core i7-620M with two cores at 2.67 GHz.

Conclusion

Although I find the names a bit confusing, Intel has done a good job of separating its processors into categories to help you make a quick decision. If you want the most affordable option, choose a Core i3. If you want the most value for money, choose a Core i5. If you want the most performance currently available, choose a Core i7.