How to Compare Different CPUs the Right Way

The Central Processing Unit (CPU), also known as a processor, is the brain of the computer and is thus the most important component. Unfortunately, comparing two different processors side-by-side can be tough, which can complicate any purchases you might make.

The bad news is that you can’t just rely on clock speed or cores, which are the two most heavily advertised aspects of processors. The good news is that you don’t need to know how a CPU works, although that can prove useful.

The other good news is that there are sites out there that make such comparisons easier. In this article, we’ll tell you exactly what matters and what doesn’t when comparing different processors, and how to compare them the right way.

Clock Speed Isn’t Everything
Clock speed and cores are the most heavily advertised aspect of processors. Clock speed is usually noted in hertz (e.g. 3.14 GHz) while the number of cores is usually advertised as dual-core, quad-core, hexa-core, or octa-core.

For a long time, it was this simple: the higher the clock speed, the faster the processor, and more cores meant better speeds. But processor technology today isn’t dependent as much on the clock speed and cores because CPUs now have several other parts that determine how fast they can perform.

In a nutshell, it comes down to how much computing can be done when all parts of a CPU come together in a single clock cycle. If performing Task X takes two clock cycles on CPU A and one clock cycle on CPU B, then CPU B might be the better processor even if CPU A has a higher clock speed.

Compare clock speeds only when you are trying to decide between two CPUs from the same family and same number of cores. What this means is that if you’re looking at two quad-core Intel Core i5 Skylake processors, then the one with the higher clock speed will be faster.

For any other scenario, the clock speed or cores don’t always indicate performance. If you’re comparing Intel Core i3 vs. Core i5 vs. Core i7 processors, then clock speed and number of cores don’t matter. And if you’re comparing Intel vs. AMD or an AMD A10 vs. AMD A8 vs. AMD FX, then clock speed alone won’t tell you much.

Check Single-Threaded Performance
The dirty little secret in the computer world is that even though you’re buying a processor with four cores, all four of those cores might not actually be used when you’re running applications.

Most software today is still single-threaded, which means the program is running as one process and a process can only run on one core. So even if you have four cores, you won’t be getting the full performance of all four cores for that application.

That’s why you also need to check the single-threaded (or single-core) performance of any processor before buying it. Not all companies explicitly release that information, so you’ll need to rely on third-party data from reliable resources like Passmark benchmark tests.

Passmark’s full list of CPU benchmarks has a single-threaded rating for each CPU.

Cache Performance Is King
The cache is one of the most under-appreciated parts of a CPU. In fact, a cache with poor specs could be slowing down your PC! So always check the cache specs of a processor before you purchase it.

Cache is essentially RAM for your processor, which means that the processor uses the cache to store all of the functions it has recently performed. Whenever those functions are requested again, the processor can draw the data from the cache instead of performing it a second time, thus being faster.

Processors have different levels of cache, starting with L1 and going up to L3 or L4, and you should only compare cache size at the same level. If one CPU has L3 cache of 4 MB and another has L3 cache of 6 MB, the one with 6MB is the better choice (assuming clock speed, core, and single-threaded performance are all comparable).

Integrated Graphics Matter, Too
Intel and AMD have combined the CPU and the graphics card into an APU. New processors can usually handle the graphics requirements of most everyday users without requiring a separate graphics card.

These graphics chipsets also vary in performance depending on the processor. Again, you can’t compare an AMD to an Intel here, and even comparing within the same family can be confusing. For example, Intel has Intel HD, Intel Iris, and Intel Iris Pro graphics, but not every Iris is better than HD.

Meanwhile, AMD’s Athlon and FX series come without graphics chips but cost more than the APU-centric A-Series, so you’ll have to buy a graphics card if you’re getting an Athlon or FX processor.

In short, graphics processing on CPUs is still quite confusing, but you still need to pay attention to it! The best option is to consult third-party benchmarks and look for recommendations.

Futuremark developed the 3DMark graphics test, which is one of the best free Windows benchmark tools out there. You can check the 3DMark Physics Score of any processor and compare it to others in Futuremark’s processor list, which should give you a fair idea of which CPU has better graphics.

The Best Way to Compare CPUs
All of these factors come together to make CPU comparisons a difficult proposition. How do you know which one you should buy? Here are a few tips that may help.

The easiest and best way is to head to CPUBoss. This site compares two processors and gives ratings and explains the differences between the two in terms that any non-techie can also understand.

CPUBoss doesn’t perform its own benchmarks, but instead collates them from different sources like PassMark, PCMark, CompuBench, GeekBench, SkyDiver, and more. It basically saves you the trip of going to many sites.

The CPUBoss score is a safe parameter in making your purchase decision, with the simple idea that whichever processor scored higher is the better one. CPUBoss also compares integrated graphics, telling you which APU has the better graphics performance.

In case you are looking for more details than what CPUBoss provides, I’d recommend the AnandTech CPU Benchmark Tool. Here you can browse in-depth benchmarks conducted by one of the best independent hardware review sites and even compare two processors side-by-side.

Other Factors That Affect Performance
When it comes to overall performance, keep in mind that your processor is only as good as the rest of the hardware. If you buy a great processor and only stick in 2 GB of RAM, then it will be bottlenecked in speed.