Multi-GPU setups provide the best graphical performance, and here’s how to get the best from the tech
Most people may be content with a single graphics card; some are even happy with onboard video. However, as PCs have evolved, and games have become more and more complex and visually accomplished, the need for power has grown. Graphics cards have become more and more powerful as a result, allowing developers scope to produce the best graphics they can, in fact, the more powerful graphics cards can even help the main CPU with its own workload, boosting your PC’s capabilities.
One of the biggest advances in PC graphical tech, however, has to be the introduction of multiple GPU systems. This is the ability to install more than one graphics card inside a PC, connecting them together to function as a single, more powerful unit. It’s kind of like the graphical equivalent of Voltron or, for younger readers, the Power Rangers.
By connecting two or more GPUs together via their corresponding interface (Nvidia and ATI have different connections), you increase the graphical power of the system by two – or more, if you go for an even more impressive setup. The system has the ability to utilise all of your cards’ power, thus allowing more impressive detail, higher frame rates, and a generally superior performance.
Of course, it’s not as easy as just buying two (or more) cards and installing them. There are other considerations you need to take into account and, once installed, there are further steps you can take to get the most out of your new multi-GPU setup. So, let’s take a look.
Is It Worth It?
The first question you need to ask yourself when considering a multi-GPU setup is whether it’s worth the hassle. The answer to this will depend greatly on your use for the PC. If you’re not a gamer, or power user, then no, of course it’s not. If you simply use your PC for social media and Internet browsing, maybe even a little multimedia, you’ll probably not even be pushing your current, single-GPU setup. This being the case, it’s not worth to time, effort, and more importantly, cost.
However, if you’re reading this, and if you’re thinking about multi-GPU options, it’s probably safe to say you’re into gaming at the very least, in which case, multi-GPUs are undoubtedly worth it. There are many reasons for this, with the chief one being the guaranteed boost in graphical horsepower. This will give you a huge leap in speed, texture detail, FPS, and more. You’ll be able to run games at very high detail levels and resolutions, whilst still maintaining a smooth frame rate. Dual and higher card setups are also a great idea if you’re planning to run at 4K resolutions, so it’s well worth considering this if this is the case.
What’s more, if you shop around, there’s no need to spend a fortune. Even two mid-range cards will usually yield great results, so you don’t necessarily need to spend large amounts of cash on the best, high-end models. Depending on your current system, though, you may need to upgrade your motherboard.
Preparations
In order to utilise a multi-GPU setup you’ll first need a motherboard that’s capable of handling this. If your system isn’t that old, you’ll probably already have the option to install at least two GPUs, but it’s always worth checking before you rush out to buy a couple of new GPUs.
It’ll be very apparent, as your documentation will clearly state this, along with the kind of dual GPU tech the board supports. The board will also have ample space for additional GPUs. The two main options here are Nvidia’s SLI (Scalable Link Interface), and ATI’s Crossfire. These are similar technologies, but deal with each of the vendor’s hardware, so be sure to check which your board supports. Many will handle both, but you should check just to be certain.
Another important consideration is your PC’s case. You’re going to need a case that has enough room to house the multi-GPU setup, and if you plan to buy high-end cards, which are usually much larger in size, you’ll need plenty of room not only to accommodate the cards themselves, but also to help with airflow, as you’ll be generating a lot of heat (which we’ll come to later).
Additionally, you should double-check your power supply specifications, and ensure that it can provide enough power to your system. If you use a limited PSU, you’ll run into problems. A rough recommendation would be at least 800-1000W, but this can vary depending on the hardware you choose.
Assuming this is all taken care of, you’re free to go looking for your multiple GPUs., but you need to take into account the limitations of SLI and Crossfire tech. Both deal with GPUs differently in terms of mixing and matching graphics cards. Crossfire is a little more flexible, whilst SLI is not as forgiving.
If you’re using Nvidia’s SLI tech you’ll need to ensure that your GPUs are the same model, as mixed models won’t work. The models can be from different manufacturers, though, as long as you ensure the model is the same. So, for example, you could use a GTX 460 from Asus and a GTX 460 from Gigabyte together, but not a GTX 460 and a GTX 470, as the model and chipset is different. It’s also important to note that one card can be overclocked, whilst the other isn’t (again, more on this later), but the overclocked card may be slowed to match to other, nonoverclocked card.
For ATI’s Crossfire you can be a little more flexible. Here you can mix and match different models, as long as they’re in the same series. So, you could use a 7950 model with a 7970, but not a 7850 with a 7950, as this include card from two different series.
Simple Things
Once you have your cards, and have installed them in your PC, you’ll probably hit one of the most common questions first-time multi-GPU users ask: which of the cards you should connect to the monitor?
The short answer here is ‘any’. It doesn’t actually matter which of the cards you connect to your display, as all cards are connected and shared by the system, so any will work fine. However, there is a more detailed answer that you may want to consider in terms of getting the most from your multi-GPU setup, and it involves overclocking and heat.
In most systems, the top-most of your GPUs will be the one that experiences the most heat build up. This is because, as any school kid knows, heat rises. If you’re running overclocked cards, this will only exacerbate the situation. When you pair this with the monitor connection, it can make things even worse. As the card connected to the monitor is going to be doing slightly more work, as it has to actually output the image, it’ll generate a little more heat. It’s negligible, but it’s there. For this reason, many expert users choose to connect their display to the lower card, as this is usually the coolest, and therefore helps keep your system that little bit cooler.
Indeed, cooling should be a major concern if you’re going to run multiple GPUs, as you’ll generate a lot more heat. Aside from the main CPU, graphics cards will generate the most heat in your system, so having more than one will greatly increase the hot air you’ll need to shunt out of your PC. Because of this, you’ll probably need to invest in better cooling. If you have a large enough case with good airflow, you should be able to fit more case fans, and this is important, especially so if you plan to overclock, which is one of the best ways to get the most from your multi-GPU setup.
Overclock
Having multiple GPUs installed will instantly give you a better level of performance than a single card, so right from the off you should be happy. However, now that you’ve spent more money, and spent the time setting up the system, why not get even more out of it, for free? Overclocking isn’t anything new, and most PC users will be familiar with it. It’s also a great way to increase your multi-GPU performance, easily gaining more general performance and an increased frame rate. To do this, you’ll need a good overclocking program designed for GPUs. Both Nvidia and ATI have such programs, which you can download from the respective websites, but you can also get other vendor-specific models that’ll work with other cards. A popular, and very easy to use example is EVGA’s Precision. This can be grabbed from www.evga.com. You’ll need an active registered account to download it, but this is free. Once you register, you can download and install the tool.
The program features an attractive speedometer-style interface, and all you need to do to make changes is use the various sliders to alter your card’s settings. Sliders deal with fan speeds, voltage, power and temp targets, clock speed, and memory clock speed. You can instantly test settings out, apply them, or set them back to default. Several profiles can also be set up and saved, so you can create different overclocking configurations for specific tasks. The program also lists each GPU installed in your system in the bottom-right.
When you begin to experiment here, always heed the oldhand overclocking mantra of slowly, slowly. Don’t be tempted to simply max out your GPU and memory speeds, as this may simply end up making your system unstable. Instead, you have to take a slow, careful approach, gradually increasing clock speeds and testing them until the system becomes unstable. This way, you find your hardware’s limits, and you’ll know how much you can safely push your hardware. With this in mind, let’s take a look at the specific settings.
First we have the fan speeds. This will deal with the fan speeds mounted on your GPUs. Usually, you’ll want a higher speed here, as this will have he best affect of system cooling. However, it’ll also make more noise and use a little more power. If you’re really pushing the hardware, though, keep this high.
Increased voltage can help deliver better results, as more power supplied to the hardware will enable it to operate at higher speeds. This will, of course, generate more heat, however, and some hardware simply isn’t designed to handle higher voltages, and in a worst case scenario, you may cause damage. This is one setting you really need to use carefully, making slow increases.
The power and temperature targets are set to allow the software to throttle back settings if needed. For example, if the temperature target is exceeded, meaning too much heat is generated, setting will be throttled to generate less heat.
The most important settings, though, are GPU Clock and Mem Clock. These deal with the currently set GPU and Memory clock speeds, and by increasing them you can squeeze out extra performance from your hardware. To do so, simply move the sliders to increase the speeds in small increments, and then test each. This is best done with some form of benchmark program running, so use whichever one you prefer and observe for any performance increases. Benchmarks are also useful for spotting problems, such as graphical artefacts due to overheating, slow performance, or instability.
Going back to the voltage setting, some users will also use less power for various reasons, one being the generation of much less heat. This is a good tactic, but is also a problem, as too little power can also cause instability, and at the very least, will negatively impact performance.
Other simple tips for overclocking include performing the actual overclocking in a cool room, perhaps with your case open. This won’t reflect general use, and you do need to test this, but it makes for a safer test bed to work with your first couple of times, until you get more experienced and what your PC’s limits are. It’s also a good idea to have a couple of actual games installed and ready to go, particularly graphically demanding ones. Benchmark tools are great for evaluating your GPU’s performance, but there’s no better way to test your changes out than to actually play a game. So, do this in between increments to see what actual, practical improvements you’re making.
Be aware that increasing memory speed will give you some increases in performance, but not as much as the actual GPU clock, and memory speeds will also require more power. Some users prefer to leave this in order to save power, but this is subjective, and there are differing opinions.
By gradually increasing the speeds, you’ll end up with even more power from your multi-GPU setup, meaning you’ll have no problems running games at their very best.