What is a CPU?
A central processing unit (CPU) is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions. The computer industry has used the term “central processing unit” at least since the early 1960s. Traditionally, the term “CPU” refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry.
The form, design and implementation of CPUs have changed over the course of their history, but their fundamental operation remains almost unchanged. Principal components of a CPU include the arithmetic logic unit (ALU) that performs arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that orchestrates the fetching (from memory) and execution of instructions by directing the coordinated operations of the ALU, registers and other components.
Most modern CPUs are microprocessors, meaning they are contained on a single integrated circuit (IC) chip. An IC that contains a CPU may also contain memory, peripheral interfaces, and other components of a computer; such integrated devices are variously called microcontrollers or systems on a chip (SoC). Some computers employ a multi-core processor, which is a single chip containing two or more CPUs called “cores”; in that context, one can speak of such single chips as “sockets”. Array processors or vector processors have multiple processors that operate in parallel, with no unit considered central. There also exists the concept of virtual CPUs which are an abstraction of dynamical aggregated computational resources.
While some of the more computer savvy among us might be well aware of the differences between a central processing unit (AKA CPU) and the graphics processing unit (GPU), most of us really only know one thing about them — the CPU handles most of the computer processing except some of the more intense graphics processing which is handled by the GPU. Beyond that, however, there are quite a few important differences to keep in mind.
What Is a GPU?
The GPU’s advanced capabilities were originally used primarily for 3D game rendering. But now those capabilities are being harnessed more broadly to accelerate computational workloads in areas such as financial modeling, cutting-edge scientific research and oil and gas exploration.
In a recent BusinessWeek article, Insight64 principal analyst Nathan Brookwood described the unique capabilities of the GPU this way: “GPUs are optimized for taking huge batches of data and performing the same operation over and over very quickly, unlike PC microprocessors, which tend to skip all over the place.”
Architecturally, the CPU is composed of just few cores with lots of cache memory that can handle a few software threads at a time. In contrast, a GPU is composed of hundreds of cores that can handle thousands of threads simultaneously. The ability of a GPU with 100+ cores to process thousands of threads can accelerate some software by 100x over a CPU alone. What’s more, the GPU achieves this acceleration while being more power- and cost-efficient than a CPU.
CPU Vs GPU
Most recently, a new computer chip has also been created — the APU, or Accelerated Processing Unit. This combines a CPU and GPU into one architecture, essentially taking on every single action your computer requires. No, it’s not an integrated graphics processor — it’s simply one processor for everything. The advantage of this is that it reduces the transfer rate between the CPU and GPU and uses far less power.
intelOne of the best ways to figure out the difference between a CPU and a GPU is by looking at the specs. Let’s take a look at some top-tier CPU and GPU specs.
The Intel Core i7-7500U has a base clock speed of 2.70GHz and 2 physical cores with 4 threads per core.
The NVIDIA GTX1080 GPU has a base clock speed of 1.60GHz and a hefty 2560 cores.
Based on those specs you can probably see two key differences — CPUs have a faster clock speed while GPUs have more cores. In other words, CPUs are best at handling single calculations extremely quickly, while GPUs are better at handling multiple calculations when time might not be as big of a deal.
In fact, more and more, GPUs are being used for things beyond simply rendering graphics — such as financial modeling, scientific research, and so on.
Another difference is that while processors generally don’t have their own RAM, GPUs often do, and its called VRAM. This RAM is often faster than system RAM, as its implemented on the same chip, however it’s generally a lot smaller in size. When the VRAM on a GPU isn’t big enough, it will load resources onto system RAM instead, however as mentioned that’s a lot slower than VRAM. Most graphics cards include at most 4GB or sometimes 8GB of VRAM, however as graphics get more intense and virtual reality becomes more prominent, we’re likely to see cards with more VRAM.
GPU vs CPU Performance
A simple way to understand the difference between a GPU and a CPU is to compare how they process tasks. A CPU consists of a few cores optimized for sequential serial processing while a GPU has a massively parallel architecture consisting of thousands of smaller, more efficient cores designed for handling multiple tasks simultaneously.
There are other difference between the CPU and GPU too. The CPU, for example, has an architecture that includes a lot of cache memory, which enables the CPU to handle just a few threads at a time. A GPU, on the other hand, will have a much smaller amount of cache memory which is largely dedicated to making up for a higher latency from a computer’s system RAM. As GPUs have been developed, they have included increasingly large caches that are able to do much more general things — like instructions for shaders.
While there are plenty of differences between a CPU and GPU, there are also a ton of similarities. In the end, it’s really the CPU and GPU working together that produces the best results — a truly powerful computer will have both a good CPU and a good GPU.