At one point, our computers had a central processing unit (CPU) with a single core. These days, most CPUs you’ll come across are dual core, quad core, or even octo core. We’ll explain exactly what a core is, dual core vs quad core, and how this all impacts your real-world computer usage.
The answers aren’t just helpful for leaning more about your computer — you may have to choose between a less-expensive CPU with fewer cores or a more-expensive CPU with more cores when buying a laptop, tablet, or even a smartphone. Knowing the difference between dual core vs quad core CPUs – and what it means for you – will help you make smart decisions when purchasing new hardware.
What Is a Core?
Each CPU “core” is actually a separate central processing unit, which is the part of the CPU that actually does the work. For example, a dual-core chip may look like a single CPU chip, but it actually has two physical central processing units on the chip.
Additional central processing units allow a computer to do multiple things at once. If you’ve ever used a single-core CPU and made the upgrade to a dual-core CPU, you should have noticed a significant difference in how responsive your computer is.
For example, let’s say you’re extracting an archive file and browsing the web at the same time. If you had a single-core CPU in your computer, web browsing wouldn’t be very responsive. The single core would have to split its time between web browsing and file-extraction tasks. If you had a dual-core CPU with two cores, one core would work on extracting the file while the other core did your web-browsing work. Web browsing would be much faster and more responsive.
Whether you’re doing multiple things at once or not, your computer is often doing system tasks in the background and you can benefit from additional cores to keep the operating system responsive. Applications can also be written to take advantage of multiple cores. For example, Google Chrome renders each website with a separate process. This allows Google Chrome to use different CPUs for different websites rather than using a single CPU for all browser-related tasks.
Clock Speed vs. Cores
CPUs have a clock speed – think of it as how fast the CPU does work. (That’s actually an imperfect analogy as the truth is a lot more complicated, but it will have to do for now.)
For example, Intel’s Core i5-3330 processor has a clock speed of 3 GHz and is a quad-core processor, which means it has four cores. All four cores in this Intel i5 processor are each running at 3 GHz.
Doubling The Cores Doesn’t Double The Speed
Many computer programs are single-threaded, which means that their work can’t be divided across multiple CPUs. They must each run on a single CPU. This means that doubling the cores won’t double their performance.
If you have a single-threaded application running on a 3 GHz quad-core CPU, that application will run at 3 GHz — not 12 GHz. It will use one core and the other three cores will sit idle, waiting for other tasks to perform.
Writing properly multithreaded applications that can scale across several CPUs at once is actually a difficult problem in computer science. It’s becoming a more crucial problem, as the future looks to be computers with more and more cores instead of fewer cores at faster and faster speeds.
Some applications can take advantage of multiple cores. Google Chrome’s multi-process architecture allows it to perform actions across several different cores at once. Some computer games can divide their calculations across multiple separate cores at once.
However, most of the applications you use are likely single-threaded. A quad-core CPU won’t run Microsoft Office twice as fast as a dual-core CPU. If all you do is run Microsoft Office, the performance might be extremely similar.
More cores help if you’re looking to do more at once or if you have a multithreaded application that can take advantage of them. For example, if you’re running several virtual machines while encoding video, extracting files, and doing other CPU-demanding things on your computer, an octo-core CPU may be able to keep up while even a quad-core CPU may stumble under such load.
Dual Core, Quad Core & More
Phrases like “dual core,” “quad core,” and “octo core” all just refer to the number of cores a CPU has:
- Dual Core: Two cores.
- Quad Core: Four cores.
- Hexa Core: Six cores.
- Octo Core: Eight cores.
- Deca Core: Ten cores.
Controlling & Monitoring Cores
You can actually control which running programs can use a core from the Windows task manager. Right-click a process on the Processes pane and select Set Affinity.
You’ll be able to select which physical CPUs (cores) the application can run on. You shouldn’t need to tweak this most of the time, although it can be helpful when you want to restrict a demanding application to certain cores or avoid bugs in old PC games.
From the task manager, you can also use the Performance tab to view the usage of all your CPU cores.
Hyper-Threading
Intel CPUs use a technology referred to as “hyper-threading technology.” With hyper-threading, each physical core presents itself to the system as two logical cores. In the screenshot above, we’re not using an octo-core CPU – we’re using a quad-core CPU with hyper-threading.
This improves performance to some degree, but a quad-core CPU with hyper-threading is nowhere near as good as an octo-core CPU. You still only have four physical cores, although some tricks allow them to do a bit more work at once.
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