While many people pay attention to the speed of their computer’s CPU (central processing unit) and how much RAM (random-access memory) their applications need, the video card (also called the graphics card) is getting more attention as image-editing, video-editing, and game applications increasingly rely on it. In addition, today’s desktop displays are larger than ever, and a new wave of high resolution monitors such as the Apple Retina display have a dramatically increased pixel density (pixels per inch resolution) that has also increased the number of screen pixels that need to be managed for a given screen size. All of these changes add to the work that a video card has to do.
(Note: This article covers how graphics hardware works on Macs using Intel processors. Macs using Apple Silicon processors work differently, and that is not covered here. I may cover that after I gain a better understanding of the differences.)
But how do you know if your current video card has enough memory? This article covers:
- Why is video RAM important?
- How can you measure video RAM usage on a Mac?
- Can you add more VRAM to a Mac?
- How do you know how much VRAM is available for Macs with integrated graphics?
- Is your Mac video hardware good enough for Adobe software? (with links to Adobe GPU FAQs)
- Can I upgrade my Mac graphics capability with an external GPU?
I have updated this article since it was first written.
Why is video RAM important?
In the same way that a computer has a CPU (central processing unit) that interacts with RAM (random-access memory), a video card has a GPU (graphics processing unit) that works with VRAM (video random-access memory). The primary mission of the video card is to drive your displays and make graphics show up faster on those displays.
On low-end computers, the GPU is often on the same chipset as the CPU; this is called integrated graphics or integrated video. Any memory needed for graphics is taken from the main system RAM (see details about VRAM amounts on Macs with integrated video). On high-end computers the CPU and GPU are separate chipsets, each with their own memory; this is called discrete graphics or dedicated graphics. This design allows more powerful GPUs to be used, and with more VRAM. In a desktop computer, the GPU and VRAM are often on a completely separate card that can be easily replaced.
Today’s video cards are so powerful that many applications now use the GPU to get through photo and video processing and effects faster, which also frees up the CPU to process other things at the same time. The power of the GPU has helped make it possible for affordable computers to smoothly edit HD video, high-resolution stills, and 3D graphics and animation. For these reasons, you see video card specs creeping into the system requirements of more software such as Adobe Photoshop, Adobe Lightroom Classic and Lightroom, Adobe Bridge, and Adobe Premiere Pro. Earlier versions of Photoshop limited GPU acceleration to document navigation (such as smoothly panning and zooming very large documents) and 3D, but Photoshop versions starting with CS6 now uses the GPU to speed up additional features such as Liquify.
How can you measure graphics hardware usage on a Mac?
Activity Monitor, the standard macOS utility for monitoring the system, recently added a GPU tab so you can see which applications are using the graphics hardware the most.
In addition, you can choose Window > GPU History to see a graph of GPU usage over time. In the example below, the top shows the internal integrated graphics of my 13″ MacBook Pro, and the bottom displays the discrete graphics card in an eGPU connected using Thunderbolt 3, while using GPU-accelerated features in Adobe software. The integrated graphics aren’t being used because the discrete graphics card is so much faster and more powerful. If I disconnect the eGPU, the bottom graph goes away and the Intel Iris Plus graph becomes very busy instead.
Starting with iStat Menus 3.1.6, you can see graphics usage in the CPU & GPU menu. The GPU section is most of the way down the menu. It has a bar graph of the amount of VRAM being used and it names the graphics in use. For example, my 2011 15″ MacBook Pro has both Intel HD Graphics 3000 (integrated with the CPU) and an AMD Radeon HD 6750M (discrete GPU), and in the figure below you can see that the discrete Radeon is currently active because at least one running application, such as Photoshop, caused discrete graphics to activate.
But what does it all mean?
You can watch a graphics hardware utility as you use different applications or change your monitor settings. If the amount of VRAM in use is always well below 100% then your current video card is fine. But if the VRAM usage is consistently near 100%, your Mac might run GPU-accelerated applications faster if you switch to a video card with more VRAM.
Some of the general factors that can increase VRAM usage are:
- Larger displays and multiple displays. It takes more graphics card memory to display more pixels. Connecting an external monitor will use more VRAM because you increase the number of pixels to update. I believe that adding Spaces (macOS virtual desktops) has a similar effect on VRAM as adding displays.
- Higher pixel density. Retina/HiDPI displays, including 4K/5K desktop displays, pack many more pixels into each square inch than a traditional display. That increased pixel density requires more VRAM.
- Larger documents and multiple documents. The more graphics documents you have open, the more video RAM it takes to manipulate them.
- 3D. Applications with 3D features commonly have them handled by the GPU and its VRAM. For example, if you use the 3D features in Photoshop or Adobe After Effects, the VRAM and 3D capabilities of your card matter more than if you only edit 2D images.
- GPU-accelerated features. Certain features use the GPU to perform dramatically faster, such as Liquify in Photoshop or the Mercury Graphics Engine and many effects in Adobe Premiere Pro. Features like these often need a specific GPU and a minimum amount of VRAM to achieve the speed boost, so check their graphics card requirements to make sure that the card in your computer qualifies.
Given those general guidelines, keep in mind that it’s possible for two Macs with the same specifications to have very different VRAM usage patterns if different features, document sizes, and display resolutions are used. Also, some recent MacBook Pros have two sets of graphics hardware that they automatically switch between: integrated graphics (the GPU is part of the CPU) for optimal battery life, and a dedicated video card with its own additional VRAM that kicks in when a specific application needs high-performance graphics.
As of 2020, more applications are adding or improving their support for GPU acceleration, so for applications that are important to you, check their system requirements with each upgrade to see if GPU acceleration might make more of a difference.
Can you add more VRAM to a Mac?
The ability to increase the VRAM for your Mac depends on whether it has discrete graphics, integrated graphics, or a Thunderbolt 3 port.
On Macs with discrete graphics, the only model that makes it possible to upgrade the amount of discrete VRAM built in is the Mac Pro tower desktop. In that type of Mac the video card is in a standard expansion slot so it can be easily replaced with a better one. In Mac OS X 10.8.3 or later you can use a wide range of PC graphics cards in an aluminum Mac Pro; it used to be that you could only use graphics cards specifically flashed for Macs. One place to find a wide range of Mac Pro-compatible graphics cards is the online store macvidcards.com (that’s just a suggestion, as I have no experience or connection with that store).
Unfortunately, the graphics hardware in all other Macs—desktops and laptops—can’t be upgraded, either because they have graphics cards permanently soldered to the motherboard or because the graphics are completely integrated with the CPU, which also can’t be replaced.
On Macs with Thunderbolt 3 ports, it is possible to use a graphics card in an external case. This is called an eGPU, or external graphics processing unit, and it becomes a way to add more VRAM to the Mac by using whatever amount of VRAM is on that external graphics card.
On Macs with integrated graphics, because graphics hardware uses the same RAM as the system it may be possible to increase VRAM by adding more system RAM. But how it works depends on which Mac you have and which version of OS X it’s running, and to learn about that you want to read the next section.
How do you know how much VRAM is available for Macs with integrated graphics?
(I added this info in June 2013) When a computer has discrete graphics, the amount of VRAM it has is fixed and usually clearly stated. When a computer has integrated graphics it’s harder to tell how much VRAM it can use, partly because the graphics hardware doesn’t have its own memory. In addition, in some systems the amount of VRAM used by integrated graphics varies depending on how much RAM is installed. This has made the amount of VRAM in Macs with integrated video a bit of a mystery when you’re trying to figure out if you can run specific software that requires a minimum amount of VRAM. Now Apple has published a tech note detailing how much system RAM is allocated to VRAM for specific Mac models that have integrated video, and here is the link to that:
That tech note contains several important lessons. First, for some Macs with integrated graphics, the only way to maximize the amount of VRAM is to upgrade the amount of system RAM. Note that in some models, VRAM will increase only up to an amount of RAM that’s lower than the maximum that Mac can take; beyond that point adding more RAM doesn’t increase VRAM any further.
Apple’s tech note also shows that that Macs with both integrated and discrete graphics hardware may have a lower VRAM amount available when using integrated graphics than Macs that have integrated graphics only. My take is that this is not a disadvantage at all, because on Macs with dual graphics hardware, macOS probably figures that if your graphics needs are getting that serious it might as well switch over to the faster discrete graphics processor that also has its own VRAM. Being able to use the VRAM of the discrete graphics hardware lets macOS release the RAM that was being used as VRAM, so more RAM becomes available to you.
The end of the Apple tech note also describes the graphics performance benefits of making sure you install matched pairs of RAM modules.
[Note (October 22, 2013): OS X 10.9 Mavericks improves how Macs work with integrated graphics. It can dynamically adjust the amount of RAM allocated to VRAM to respond to changing application requirements, including the ability to release VRAM back to RAM when it isn’t needed for graphics. Also, you no longer necessarily need discrete graphics hardware to use OpenCL graphics acceleration, because Mavericks can run OpenCL on Intel HD Graphics 4000 or better. Some applications may have more stringent requirements for OpenCL graphics acceleration. For more details about all of these improvements, read the excellent article OS X 10.9 Mavericks: The Ars Technica Review by John Siracusa.
Is your Mac video hardware good enough for Adobe software?
Adobe has been increasing its use of graphics hardware to help accelerate its software. Here are links to graphics requirements for some Adobe applications:
- Adobe Photoshop GPU FAQ
- Adobe Photoshop CS6 GPU FAQ
- Adobe Camera Raw GPU FAQ
- Adobe Lightroom Classic GPU FAQ
- Adobe Premiere Pro GPU FAQ
If you’re trying to decide on graphics options for your Mac, keep in mind that you don’t necessarily need expensive high-end graphics. For photography and design in Adobe applications, the amount of video RAM is more important than the sheer power of the video card, and much less graphics power is needed than for serious gaming. But the more you edit video or use 3D, the more you may need a video card with additional processing power. Note that Adobe Lightroom Classic uses GPU acceleration for the Develop module only, where in my experience it makes a big difference, but for now the rest of Lightroom is more CPU-based.
In older versions of Adobe software, GPU acceleration largely focused on the CUDA technology in NVIDIA graphics hardware. Most GPU-accelerated Adobe applications added support for more widely available OpenCL technology, which vastly expanded the range of supported graphics hardware that Adobe software can use for GPU acceleration. For Macs, this is important because macOS does not currently support CUDA graphics. Adobe is now moving away from OpenCL and OpenGL, and toward newer graphics technologies such as Apple Metal.
One nice side effect of Adobe adding GPU support beyond CUDA is that most GPU acceleration no longer requires discrete graphics. The Intel Iris integrated graphics found in much of the Mac product line now qualifies for GPU acceleration in many applications including Adobe Premiere Pro and Adobe Lightroom Classic. However, if you spend a lot of time editing and rendering video or large graphics files or photographs, discrete graphics acceleration still provides a much bigger boost.
Can I upgrade my Mac with an external GPU?
[Added April 2017, updated October 2020] With the high bandwidth available through Thunderbolt 3, it’s now possible to create a graphics upgrade solution involving a desktop-class video card in an external enclosure connected to a PC or Mac with a Thunderbolt cable. Many Mac users wonder whether it’s possible to upgrade their Mac’s graphics capabilities this way.
Apple added limited support for eGPUs in macOS 10.13.4 High Sierra, only for Macs with Thunderbolt 3 ports. (See Use an External Graphics Processor with Your Mac at apple.com.) That support was improved in macOS 10.14 Mojave and macOS 10.15 Catalina, to the point where I now use an eGPU to boost the relatively weak performance of the integrated graphics in my 13″ MacBook Pro. I bought a graphics card and an eGPU case only after looking at how much the applications I use the most take advantage of the GPU (see the FAQs above), and determining whether the work I do would actually benefit from it. Remember, a GPU accelerates only features that depend heavily on graphics performance, and many features are still CPU-based.
The cost of currently available solutions adds up after you factor in the cost of both an eGPU enclosure ($200–400) and the video card you want to put into it ($200 to beyond $1000). Also, budget $50 or more for a Thunderbolt 3 cable if you want it to be longer than meter. Short distances can be covered with an inexpensive passive cable, but longer distances require a more expensive cable. The very high throughput of Thunderbolt 3 requires a tight cable specification, and longer distances require an active cable (cable with electronics), pushing up the price.
Also, an eGPU is often not a good solution if you want to use the most powerful graphics cards. The reason is that Thunderbolt 3 has a maximum theoretical bandwidth of 40Gb (gigabits) per second, and although that is much faster than USB 3, the most powerful graphics cards are faster still, and are choked by that 40Gb limit. But an eGPU is fine if a low-end or midrange graphics card is good enough for your applications and displays.
The promise of external GPUs appeals very much to owners of older Macs. However, those are the Macs least able to use an external GPU. Graphics processors move so much data that external GPUs are really built for Thunderbolt 3 bandwidth, especially when driving 4K+ displays. Older Macs only have Thunderbolt 1 or 2, which may not be able to move the required amount of data fast enough. A GPU helps only if the time needed to get the data out to the GPU and back, plus processing time, is less than the time it would have taken to process the data without the GPU.
You can keep track of how well the current solutions work by monitoring Mac enthusiast web sites. One site is long-time Mac performance test site Bare Feats, which has tested a number of external GPUs.