The latest PC games require serious GPU power to experience them in the way they were intended. As a result, people usually try and get the best graphics card possible.
However, another solution is to use multiple graphics cards in the same system to increase performance. This can be far more cost effective than purchasing the latest graphics cards which can be hellishly expensive.
SLI & Crossfire are two methods of combining the power of a graphics cards. However, there are upsides and potential downs to both methods which we will be looking at now.
SLI and Crossfire are both solutions that allow a user to create a setup that involves multiple graphics cards.
However, they accomplish this in different ways, and there are some important differences between them to understand. SLI is the solution created by NVIDIA, whereas Crossfire is the solution created by AMD.
Both of these solutions offer two options for splitting the performance of the graphics cards.
The Difference Between SLI and Crossfire
There are some key differences between SLI and Crossfire in their application and specific requirements.
One of the restrictions of the SLI is that any configuration must have the same GPU to work. Although the particular brand of the card is not relevant, the GPU specification must be identical.
Note: SLI connectivity was left out of the RTX 2060 and RTX 2070. Therefore, only the 2080 and 2080 Ti from the RTX series can be connected in SLI.
Whereas, Crossfire offers more flexibility as it allows different GPUs to work together so long as they belong to the same architecture.
For example, different models of an RTX could work in the same setup. However, an RTX could not work with an R9. Although, it is still recommended to use similar model cards as this leads to better performance.
Crossfire only functions in full-screen mode, whereas SLI works in both full screen and windowed modes.
The connection requirements also differ between SLI and Crossfire. An SLI configuration requires the graphics cards to be connected with a cable, or alternatively an SLI bridge.
An SLI setup uses a ‘slave card’ and a ‘mastercard.’ The information is sent from the master card to the slave card to be processed. This requirement was also present in the previous versions of Crossfire.
However, the latest versions have the capability of communicating through PCle 3.0. This forgoes the need for a physical cable to connect the cards together. This method uses an XDMA to open a direct channel for communication between multiple cards in the system.
There is somewhat of a noticeable cost difference between SLI and Crossfire. SLI configurations tend to be more costly because of a specific certification required by NVIDIA.
This certification is not available on all motherboards and the ones that do have it tend to be costlier.
SLI does not have any similar requirement, which means that cheaper motherboards can work fine with the configuration. This also provides more flexibility as there is no need to check for any clarification.
How Does SLI and Crossfire Work
The first available option that both of these solutions offer is split frame rendering. This is where each individual GPU will share the workload of handling the processing of each frame. In a sense, the frames will be split up between the GPUs, and this will work with divided portions. Rather than being split on pixels, the frames are instead split on workload.
The other option utilizes alternate frame rendering. This method still splits up the workload, however, in the frames are pre-assigned to the GPUs. They spread the frames amongst themselves evenly.
In a dual setup, for example, the first GPU would handle frames, 1,3,5.. And the second GPU would handle frames, 2,4,6… In general, alternate frame rendering is the more common option with both SLI and Crossfire setups.
Benefits of SLI and Crossfire
The core benefit that users want to attain from using multiple graphics cards than one, is to receive more value in the form of performance. In general, it can be cheaper to use two graphics cards to achieve the same performance as using a single higher end graphics card.
So, therefore, one main reason that multiple cards are used is to get more bang from your buck.
Aside from the budget, another reason to use multiple graphics cards is to increase the maximum performance. This can be relevant during unusual scenarios where a substantial amount of extra graphic processing power is required.
It could mean running games at a maximum setting that is extremely high and one that demands a high frame rate. Alternatively, it could be attempting to run a triple monitor 4k setup.
The truth is there are very rare situations where the top graphics cards won’t cut it in terms of required processing power. The extra power that another graphics card provides can make a significant difference in performance during these situations. Dual graphics card setups can add up to a 50% increase in additional performance improvements.
Limitations of Using Multiple Graphics Cards
The core advantages of a multiple GPU setup have lessened in recent years when compared to using a single card. This is mainly because single cards have become more powerful so the need for extra processing power has diminished.
But, it is also because top range graphics cards have been relatively more affordable which has reduced the cost savings of using multiple graphics cards. Additionally, games are less optimized for multiple-GPUs.
In the past, there were specific developments in games to allow them to be perfectly compatible with a multiple card setup. Even though the latest games still perform well with setup, it is less likely to be their best performance.
One understated difference between a one card setup and multiple card setup is the hardware changes that are required for a multiple card setup to function effectively. The power consumption and heat from a multiple card setup is significantly higher which may require a cooling board and motherboard upgrades. This can raise the total cost to where the financial savings of going with a multiple card setup are diminished.
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Although, support is currently adequate for multiple graphics cards; the future of this support remains unclear. NVIDIA themselves have reduced support for dual setups in an official capacity.
This highlights that the trend of using multiple graphics cards is likely to decrease along with the support.
This leads to questions about the long-term viability of multiple card set-ups. A single card setup will be well supported for many years to come which makes it a better investment for the future. There is also the option of overclocking the GPU to get the maximum level of performance.
Which Configuration is Right For Me?
If your specific setup could benefit from multiple graphics cards, you may still be wondering if you should go with SLI or Crossfire. In general, SLI provides more consistency and is relatively more powerful. However, Crossfire adds extra flexibility since it can be used in more types of setups. SLI is usually regarded as the premium option which is recommended if you have the setup and budget for it.
However, Crossfire is still an excellent option, and its flexibility can be essential for certain setups.
If you have doubts about multiple graphics setups in general, you should conduct more research on single card setups and weight up all the costs and benefits that we have mentioned in this article.
It is important to account for all potential expenses of each option when making this decision.
Multiple graphics cards can be a great solution for increasing graphics power but only in certain situations. You will now have a clearer idea of how they work and the main differences between SLI and Crossfire.
The configuration that is right for you will ultimately depend on your situation and specific circumstances. In general, a single high-end graphics card will be a better solution than a multi-GPU setup. However, in rarer cases, a multiple setup can make a key difference and allow you to achieve maximum performance.