CPU and GPU might be familiar terms for even the most novice of computer users, but APU might be a relatively novel concept. That might’ve been the case by design, but APUs have certainly come a long way from their modest beginnings.
Before we dive into what an APU actually is, let’s first make sure we have a clear definition of both CPU and GPU.
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Central Processing Unit – CPU
Also simply referred to as the processor, the CPU is the main controlling chip in what we consider a PC. At its core, it executes basic arithmetic, logic, controlling, and I/O (input/output) operations given to it by the program. On a granular level, it’s a very simple piece of electronic circuitry which consists of the arithmetic logic unit (ALU) and control unit (CU).
The ALU is in charge of executing arithmetic and logic operations, or simply Boolean algebra, while the CU fetches data from memory and basically gives the instructions to the ALU. Below is a simple example of how an OR gate functions. When people say that computers are ones and zeroes, this is what they mean.
The CU gets data that software is in charge of sending and it determines which operations the ALU needs to do in order to deliver the desired result. The ALU then uses data stored in registers and compares them, producing an output which the CU then sends through to the appropriate location.
Of course, this is a simplified representation, as fully explaining what these things do would be steering too far away from our topic.
Nowadays, CPUs have multiple cores and multiple threads and this allows them to simultaneously perform tasks that older, single-core CPUs could not. Modern CPUs often have four or more cores (or even 16 in rare cases) which can be divided into virtual or logical cores with hyper-threading or multi-threading.
The processor’s clock speed is generally accepted as the metric of the speed of operations executed. The unit of frequency is hertz (Hz), which indicates the number of cycles executed per second. Modern computing has gotten so impressive that CPUs’ speed is measured in gigahertz (GHz), which means they can execute mind-boggling several billions of operations in a single second.
Even if 3 GHz is not enough for you, most modern CPUs can be overclocked to get even more computing power. However, note that even the most powerful CPUs out there cannot go past a certain point. The current Guinness World Record is at 8.79433 GHz – it was set way back in 2012, so it’s safe to assume it probably won’t go up too much until we get to quantum computing.
Gamers shouldn’t be too concerned about getting those super high clock rates, as even mid-range CPUs will be able to avoid bottlenecking when paired with a high-end or even enthusiast-class GPU.
The vast majority of mainstream CPUs are produced by AMD and Intel. Intel was considered king for a long time until AMD introduced the world to its Ryzen CPUs, basically revolutionizing the world of technology. Although these two are generally accepted as the best CPU manufacturers out there, it’s worth mentioning that other companies such as IBM and Apple also produce processors.
Graphics Processing Unit – GPU
Fun fact: the term GPU was coined by Sony when they launched their PlayStation console in 1994.
Due to its parallel design structure, GPU is actually more efficient than the CPU when it comes to algorithms that process large blocks of data in parallel. Of course, CPUs have more of a general purpose, while GPUs are optimized to work with specific data.
There are two main forms of GPUs: dedicated and integrated.
With a dedicated graphics card, the chip comes on a separate video card that’s removable and upgradeable. It also comes with its own dedicated RAM which is customized to work better with graphics-related processes. Dedicated GPUs interface with the motherboard via the PCIe slot.
There can also be several GPUs connected using Nvidia’s SLI or NVLink and AMD’s Crossfire, but those technologies are slowly dying out. Due to the advancement in the GPU world, it’s safe to say that there is no need for additional cards for gaming anyway.
Integrated GPUs are what the name suggests – a part of the motherboard. It uses system RAM for its operation and owing to that, it often is a lot slower than a dedicated GPU.
There are also external GPUs which are pretty self-explanatory: a GPU that’s outside the case. They connect to the PC or laptop via a mini PCIe port, ExpressCard, or a Thunderbolt port, and they’ve begun gaining traction recently. More often than not they come with their own PSU, as most laptop PSUs aren’t enough to support an external GPU, which in itself is a huge energy consumer.
Much like in the CPU market, there are two competing GPU manufacturers. While AMD is also in this market, they’re largely outshined by their rivals Nvidia. Similar to CPUs, GPUs too can be overclocked if their base clock is too slow for you.
Accelerated Processing Unit – APU
So, what is an APU then?
Actually known as AMD APU, it’s simply a marketing term for microprocessors that have both the CPU and the GPU on the same die. This might sound a little bit too similar to an integrated GPU, but there are distinctions between the two terms. The original idea for an APU started all the way back in 2006 when AMD ran a project named Fusion, but the first APU wasn’t released until 2011.
The interesting thing about the name APU is that it’s an HSA-compliant; this is the reason why Intel can’t call their integrated graphics chips that. HSA stands for Heterogeneous System Architecture, which is a set of cross-vendor sets of specifications that allow for the integration of CPUs and GPUs on the same bus with shared memory and tasks.
HSA is defined by the HSA Foundation which was founded by, you guessed it, AMD and several other vendors, Intel not included, evidently.
Intel does have an integrated GPU line, simply known as Intel HD Graphics, but as previously mentioned and largely due to its rivalry with AMD, it can’t be classified as an APU as it does not offer HSA features. Technically, HD Graphics is a combination of CPU and GPU on the same die, but due to technical differences, they can’t and aren’t considered APUs.
What makes an APU a really interesting piece of technology is the unique way in which the CPU and the GPU are combined on a single die. As such, they are able to share the same resources (including RAM), which allows them to be more effective in their use of those resources.
Another upside is that, in the long run, there is a noticeable power efficiency increase, stemming from this sharing of resources. Other advantage of this is the performance speed, as well as the decreased manufacturing cost which makes APUs have a great dollar value to its name.
Just like the CPU and the GPU, APUs can be overclocked. This comes in rather handy as APUs can be limited in performance out of the box, although it’s fair to note that you shouldn’t expect a stark improvement.
Unlike the CPU and GPU, APU’s market is a bit harder to define as AMD pretty much holds all the cards in regards to the APU patent. It’s interesting to note that APUs are most often compared to Intel’s integrated graphics line because of the similarity in the sense of GPU and CPU being on the same die, but APUs easily trump anything Intel has to offer, performance-wise.
Even though APUs originally hit the market in 2011, which in technology years might just have been a century ago, AMD has brilliantly adapted their Ryzen processors and their latest release Zen 3 got a very positive reception. At the moment, Zen 3 appears to be a lot better than anything Intel has to offer, so that is a better choice.
APU Or CPU/GPU Combo?
As always, when figuring out your next tech purchases, it’s best to fairly and precisely assess your needs and figure out the intended use for the hardware. Another key point, of course, is the budget. Getting a top-shelf gaming PC is going to cost a lot more than getting an APU.
If you’re looking for a work computer and you like to game casually with eSports games or indie titles, then APU is a great choice. What makes APU an excellent option is its ability to be upgraded. In other words, you can get an APU and if you want to play some more graphics-intensive games down the line, you can obtain a dedicated GPU and with AMD integrating its latest Zen 3 CPUs with the RDNA 2 chips to improve even further, that’s probably the best path you should be looking at.
However, dedicated CPUs and GPUs are a better option in almost any other situation. It’s just too hard for a single-die combo to compare against the separate CPU and GPU. Simply put, APU is the jack of all trades, but master of none, while both CPU and GPU are polar opposites.