Choosing the right pixel pusher doesn’t have to be hard
Buying a graphics card can be confusing at the best of times, especially if it’s been a couple of years since you last picked one up. In a world of rebranded and rebadged cards, it’s difficult to know what card does what.
That’s why the best way to make sure you find a better graphics card could be to go back to first principles and learn how to read the specifications. To help you do that, here’s our explanation of graphics card specs and how you can use them to look for a better, faster graphics card than your current one.
Chipset
A graphics card’s chipset refers to the reference design it’s based on. While graphics cards are produced by a variety of manufacturers, all cards with the same make and model number are based on a design produced by the original developer (usually AMD or Nvidia). This design is called the ‘reference design’, because individual manufacturers use it as a base to produce their own version, which may incorporate additional features or other modifications.
Importantly, all cards with the same chipset have broadly similar capabilities and can be directly compared with one another in ways that other cards can’t. If they have the same chipset, they run on the same architecture, so it’s comparatively easy to figure out which of the cards is better, because it’s usually just the one with higher numbers!
If nothing else, it’s worth paying attention to the chipset’s process design, which is given in ‘nm’ (nanometres). As with CPU architecture, the smaller this value, the more energy efficient it is, and the faster it can run.
Core Clock Speed
A GPU (graphics processing unit) core is the processor of your graphics card and the bit that performs the rendering and calculations for graphics. Most cards quote two speeds: the base clock speed (which the card normally runs at) and the boost clock speed (which it temporarily switches to at times of high load). These values are given in megahertz (MHz), similar to normal CPUs, and dictate the number of updates that the GPU can make per second.
The confusing thing about clock speeds is that they can’t be directly compared to check performance unless the chipset of the cards is the same. A card with an 800MHz clock speed can be faster than a card with a 1100MHz clock speed if the architecture is different!
If the chipset is the same, you can use clock speed to compare card performance to an extent, however. Cards with a higher clock speed perform more operations per second, so it’s not uncommon for manufacturers to perform a ‘factory overclock’ and run it slightly faster than the reference design – particularly if they add extra cooling to increase the hardware’s temperature tolerance.
Graphics Memory
It’s something of a misconception that extra graphics RAM will improve performance. Having the minimum amount of necessary RAM available is important, but if you have more than that amount, it won’t have any real effect. Far more important is the bandwidth of the memory you have available and the way it’s utilised. A 1GB card with new firmware can outperform a 4GB card with old firmware, so worry less about how much RAM is in your card and more on how well it performs. In the past the type of RAM was important, but most cards today use the superior GDDR5 type instead of the older, cheaper DDR3 type.
RAM bandwidth (which determines the amount of data that can be shifted in a single update) is affected by two factors: the memory clock rate and the memory bus size. Memory clock speeds are similar to graphics card clock speeds: the more MHz, the better the performance. Unlike GPU clock speeds, you can compare them across different cards as long as the RAM type is the same. The memory bus size is given in bits, and more bits means better performance. Most modern cards are likely to use at least a 128-bit memory bus, but you may see as high as 512-bit, with performance directly proportional to size.
As a rule, you can quickly compare available memory bandwidth by multiplying the bandwidth by the clock speed. The bigger the amount that comes out, the better.
Technology Support
All cards will quote, somewhere, which version of the two main graphics APIs they support. The latest version of DirectX is 12 and the latest version of OpenGL is 4.4. Don’t worry too much if the card you’re looking at only supports an older version. Most of the time this won’t result in any notable performance decrease; it’ll simply block off access to some of the latest effects and shaders.
Obviously, all things being equal, it’s better to have support for newer versions than not, if only because it future-proofs the card, but new versions of DirectX and OpenGL still support older cards, and it would take years for your hardware to become so old as to be incompatible with the latest releases!
Similarly, support for multi-card operation – called SLI by Nvidia and CrossFire by AMD – is only of any importance if you plan to run multiple cards in tandem. To run cards like this, the GPU needs to be the same (or have very similar underlying technology), which means that most SLI/CrossFire users buy two cards together, making it something of a moot point to consider it for future upgrades. Some low-end cards explicitly will not support SLI and CrossFire (note that Nvidia cards never support CrossFire and AMD cards never support SLI), but in general, any card at the mid-to-high end of gaming will.
Resolution & Screen Support
Fairly straightforward, the resolution support tells you how sharp an image your card can provide. It’s worth remembering that maximum resolution doesn’t tell you how usable the output will be at that size. Just because a card can provide 4K output, it doesn’t mean it can run games at a reasonable speed in 4K.
To get the most out of the card’s resolution abilities, you’ll need a screen of equivalent resolution and the proper digital interface. Note that analogue connections (such as standard VGA and DVI-I) top out at 2048 x 1536 regardless of the card you’re using.
The number and type of interfaces can also have an effect on capabilities. Here’s what you might find on a modern card: Dual-Link DVI-I / DVI-D refers to a DVI interface with extra pins that allow it to reach resolutions of 2560 x 1600, instead of the single-link maximum of 1920 x 1200. DVI-I is a combined analogue/digital port, while DVI-D is digital-only. Your card may have both or just one.
HDMI is a high-definition audio/video interface available in several different versions. The most recent pair – HDMI 1.4 and 2.0 – both support 4K video and 3D video, but HDMI 2.0 is the only to support 4K in 3D. HDMI 1.4 also only supports 24Hz refresh rate for 4K and 3D video, whereas HDMI 2.0 supports the full 60Hz.
Finally, Display Port is a video interface designed to replace VGA and DVI. With adaptors it’s backwards compatible with both ports and can also be used to carry other data such as audio and USB signals.
Usually, it’s possible to utilise several of these ports at once – sometimes up to four, depending on how many there are – so check the maximum number of supported screens. Note that some chipsets support more screens than the card can physically accommodate!
Once you know what you’re looking for, choosing a good graphics card will become a much simpler process. Now all you have to do is decide how much you want to spend!