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 monitors 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.
But how do you know if your current video card has enough memory? In this post I’ll go over a couple of tools on the Mac that can tell you a few facts about your video card, including how much memory it’s using and what kind it is. At the end of this post are links to additional information about VRAM on Macs and how much VRAM some Adobe applications need.
Why is video RAM important?
In the same way that a computer has a CPU (central processing unit) that interacts with RAM, 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 integrated with the CPU in a single chipset, and 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 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 CS6, Adobe Bridge, and Adobe Premiere Pro. Photoshop CS6 requires 256MB of video RAM and prefers at least 512MB. Earlier versions of Photoshop limited GPU acceleration to document navigation (such as smoothly panning and zooming very large documents) and 3D, but Photoshop CS6 now uses the GPU to speed up additional features such as Liquify.
How can you measure video RAM usage on a Mac?
Many Mac users know that you can monitor a lot of system information using the Activity Monitor utility, and that the System Information utility can tell you which graphics card is inside your Mac. However, one statistic you can’t get out of either utility is the current memory usage of the video card. For that, you need to turn to non-Apple utilities.
Starting with iStat Menus 3.1.6, you can see the memory usage of the video card in the menu for the CPU stats. You’ll find this in the GPU section, which is most of the way down the menu. It names the installed video card and has a bar graph of the amount of VRAM being used.
iStat Menus is USD$16, so if you don’t want to pay that much take a look at the next option…
A free alternative to iStat Menus is atMonitor. It doesn’t display GPU information in the menu bar; only in a floating palette. You can optionally make the palette stay on top of all other applications, but that means it will permanently occupy part of your screen instead of staying out of the way on the menu bar. Still…it’s free. And it displays not only the VRAM in use, but GPU activity too. (OS X 10.8 Mountain Lion users: According to the atMonitor FAQ, “To make atMonitor compatible with MacOS 10.8 we have removed all GPU related features.” The atMonitor home page says “The last version of atMonitor to support GPU related features is atMonitor 2.7.1.”) [Update, July 2014: The atMonitor site appears to be offline, I don't know why.]
But what does it all mean?
You can watch a graphics card utility such as iStat Menus or atMonitor 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 Photoshop CS6 and professional imaging 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 total display area that has to be updated. I believe that adding Spaces (OS X virtual desktops) has a similar effect on VRAM as adding displays.
- 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 Extended 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 CS6 or the Mercury Graphics Engine in Adobe Premiere Pro CS6. Features like these often need a specific GPU and a minimum amount of VRAM to achieve the speed boost, so double-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.
The only Mac model that makes it possible to upgrade the amount of VRAM is the Mac Pro, because the video card is in an expansion slot and can be easily replaced with a better one. Unfortunately, all other Macs—desktops and laptops—have video cards that are permanently soldered to the motherboard and can’t be upgraded.
If you’re trying to decide on a video card for your Mac, keep in mind that you don’t necessarily need an expensive high-end gaming card, because for photography and design in Adobe Creative Suite applications, the amount of video RAM is more important than the sheer power of the video card. Do note that Adobe applications with video-editing and 3D features may have higher graphics card requirements, so check those carefully (see GPU info at the end of this article).
If you know of any other Mac utilities that help monitor the graphics card, or if you want to suggest similar utilities for Windows, say so in the comments!
GPU info for Adobe software
Here are links to graphics card info for some Adobe applications:
- Adobe Photoshop CC and CC 2014 GPU FAQ
- Adobe Photoshop CS6 GPU FAQ
- Adobe Premiere Pro system requirements (with list of video cards supported for GPU acceleration)
- GPU (CUDA, OpenGL) features in After Effects CS6 and CC
- Enabling CUDA for Premiere Pro and After Effects in the MacBook Pro Retina
[October 26, 2012 Photoshop CS6 update: If you use 3D features and are a Creative Cloud member, those features will require 512MB of VRAM on the graphics card in future versions of Photoshop. For details, see: Heads Up: Photoshop System Requirement Changes]
GPU and VRAM info for Macs with integrated video
(New information, June 2013) When a computer has a separate graphics card, the amount of VRAM it has is fixed and usually clearly stated. It’s harder to tell how much VRAM comes with a computer that has integrated video, in part because the graphics hardware has no memory of its own since it draws from the main system RAM. 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 a few 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, OS X 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 OS X 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 example, Adobe Premiere Pro CC 2014 requires Intel Iris graphics or better for OpenCL acceleration on integrated graphics.) For more details about all of these improvements, read the excellent article OS X 10.9 Mavericks: The Ars Technica Review by John Siracusa.