Aug 04 2022

What Is an External Graphics Processing Unit?

While eGPUs are a somewhat niche technology, the devices may soon be mainstream thanks to hybrid work.

The rise of the graphics processing unit as a key element of the computing experience has been at odds with the direction that desktop computing has been going — thinner, lighter and small enough to fit in your bag.

When you want maximum performance from a GPU, it usually needs to be plugged into a wall, it’s often quite large, and it requires fans to cool it down.

That’s not to say that laptops don’t have powerful GPUs — companies such as Intel and AMD have packed increasingly powerful integrated graphics into their machines, and it’s possible to get a discrete GPU (a unit that is separate from the processor) from either NVIDIA or AMD.

But whether the ultimate goal is high-end video, 3D production work, gaming or machine learning, being able to set up a beefy GPU with a machine that’s usually portable can have its benefits. Enter the external graphics processing unit.

What Is an eGPU, and What Does It Do?

An eGPU is a GPU that can be attached externally to a computer, typically a laptop or small desktop computer that doesn’t have the space to handle a full-fledged GPU internally.

An eGPU can attach to the computer in a variety of ways; the most common uses an external enclosure for a GPU expansion card that attaches to the machine through a Thunderbolt or USB4 connector (ports that are commonly found on most modern Intel machines). Justin Chen, a product evangelist for the hardware manufacturer Razer, says the company has seen strong demand for its Core X line of GPU enclosures, which allow users to install external cards as wide as three PCIe slots in a single enclosure.

“This family of products basically handles the majority of graphics cards on the market at this point,” Chen says.

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Other approaches exist for attaching eGPUs, but they come with limitations. For example, eGPU adapters that include Thunderbolt docks, such as those sold by Sonnet Technologies, allow consumers to upgrade the graphics capabilities of older devices, but the device itself would have to be replaced with another one of similar capabilities to leverage next-generation graphics.

And while do-it-yourself approaches exist — it is not unheard of in enthusiast communities such as to attach a GPU through an m.2 expansion slot traditionally used for a high-speed NVM Express solid-state drive — they often can’t access the same level of bandwidth as a full eGPU might.

How Do They Work?

While many modern computers don’t have PCIe slots — a common interconnect method for expansion cards in desktop computers — they can still access the bandwidth set aside for those slots on modern processors through other high-bandwidth means.

Part of what enables this is the improved speed of modern connection technologies. For example, Thunderbolt is capable of 40 gigabits per second of throughput; m.2 drives are also on the PCIe bus and are capable of speeds of up to 5,000 megabytes per second, equal to Thunderbolt’s 40Gbps theoretical maximum.

For most users, it is unrealistic to use an m.2 drive to plug in external components because it would leave a mess of wires on the desk and require a power source. But an eGPU enclosure is a convenient solution, as it makes the process of plugging in parallel processing capabilities as simple as connecting a Thunderbolt or USB4 cable.

DISCOVER: Learn more about how the Thunderbolt 4 can connect your workforce.

What Are the Advantages and Disadvantages of an External GPU?

The biggest advantages of an eGPU are portability and upgradeability, allowing users who need a high-end GPU only for certain tasks (rendering videos, for example) to set the device aside when it’s not in use. Additionally, eGPUs offer a way to boost performance on computing devices that may not be the latest and greatest, which could come in handy when working with a laptop that isn’t designed to be upgraded.

There are some downsides with eGPUs, generally of a technical nature. The most significant is that users don’t get the full benefit of PCIe bandwidth, meaning they’re likely leaving some performance on the table compared with a desktop GPU implementation.

“It depends on the make and model of the host laptop, but you generally see 10 percent less performance via eGPU,” says Chen. “For most people, that’s enough, if you’re not looking to push the maximum amount of frames and turn your quality settings all the way up.”

Chen notes that while the most recent version of Thunderbolt — Thunderbolt 4 — focuses on standardization and compatibility rather than speed upgrades, future versions will likely work to improve performance. 

“Anything that comes in afterward, I think, will be an improvement to the bandwidth because that’s where things are currently,” he says.

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Another downside: As the post-production news site RedShark notes, the way the display is connected to the computer can affect performance. An internal display, like what one has on a laptop, can be difficult to implement and can cost some performance, as it requires the Thunderbolt data to make a full trip from the eGPU back to the machine, which then has to render the result through the machine’s frame buffer. With that in mind, if you decide to use an eGPU, you may want to consider using an external monitor to get the full performance of the technology.

Finally, it’s worth keeping in mind when purchasing an external graphics enclosure that GPUs have been growing in size and power consumption, meaning that if the GPU enclosure you use doesn’t support the specific power rate or dimensions your card needs, it might not work with the most recent technology.

What Type of Machines Can Use eGPUs?

Today’s eGPUs are most commonly used with Intel-based machines, such as small Next Unit of Computing (NUC) machines and other Intel laptops.

Laptops with AMD processors traditionally have not been able to use these peripherals. However, the USB4 specification, based on Thunderbolt 3, is available to any manufacturer, which would allow some AMD models to use the technology, expanding the potential eGPU user base.

While the PC market, whether Microsoft Windows or Linux, has been quick to embrace eGPUs, Apple’s shift to its own silicon-based processors have made the devices less relevant to Mac users, as Apple has chosen not to support external GPUs. However, older Intel-based Mac models can support eGPUs made by AMD, making it an option when considering an upgrade.

Justin Chen
Definitely a lot of room to grow into the mainstream market, as people will discover that there’s upcycling opportunities.”

Justin Chen Product Evangelist, Razer, Inc.

Are They Worth It?

The short answer is a qualified yes — if your use case is suitably technical and you treasure a degree of portability.

In the past, this has not always been the case. Chen points out that while Razer’s Core X line has been a consistent strong seller for the company since its 2016 introduction, it is something of a niche product, popular among college students who need a mix of portability and robust technology for both academic and leisure use. The market for eGPUs among enthusiasts has also traditionally been strong.

“Most people looking for an eGPU are already aware of the technology, so they kind of know what to look for,” he says.

However, because of the rise of hybrid work, there is potential for eGPUs to break into the wider market. Many employees who previously used desktop workstations are using laptops now; an eGPU would give them access to a powerful GPU, if needed, that could be used at home or at the office.

READ MORE: Explore the differences between Intel's high-end Core i7 and i9 chips.

“GPU availability is now beginning to return,” Chen says, citing a longstanding GPU shortage that ended only recently. “There are plenty of people now with laptops that at least have Thunderbolt level three, so you have that support.”

That means that there’s a large existing base of users that could benefit from an eGPU as a part of their work setup. 

Chen also points to the eGPU’s potential as a way to keep older computers with outdated GPUs in service. He pointed to the large market of Intel-based Apple computers that still support eGPU technology, which video producers, for example, can take advantage of.

“Definitely a lot of room to grow into the mainstream market, as people will discover that there’s upcycling opportunities,” he adds. “That's kind of a big thing, to be able to reuse, recycle and basically take something old and make it new again.”

Whatever your use case for external GPUs, if you can take advantage of them, you might soon find one sitting under your desk.

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