Introduction
When building a high-end gaming PC, one question that often comes up is whether to use a single powerful graphics card or connect two or more cards together in SLI or Crossfire. SLI (Scalable Link Interface) and Crossfire allow using multiple Nvidia or AMD GPUs together to increase performance. But is it worth it? In this article, I will compare single vs multi-GPU setups and examine the pros and cons of each to help you decide: to SLI or not to SLI.
How SLI and Crossfire Work
SLI and Crossfire use parallel processing to combine the power of multiple GPUs. Instead of rendering each frame on a single GPU, the work is split between the GPUs. For example, with two cards, one may render the top half of the frame while the other renders the bottom half.
The GPUs are connected via a bridge that allows them to synchronize and transfer data rapidly. Nvidia uses a high-speed SLI bridge while AMD relies on the PCIe bus for communication. Scaling is not 100% perfect, but overall performance is significantly boosted compared to a single GPU.
Benchmarks: Multi-GPU vs Single GPU
Numerous benchmarks have compared SLI and Crossfire performance against single powerful cards like the RTX 3090. Here are some examples:
SLI RTX 2080 Tis vs RTX 3090
- 1080p – Up to 85% faster with SLI
- 1440p – Up to 75% faster with SLI
- 4K – Only 15% faster with SLI
RX 5700 XT Crossfire vs RX 6900 XT
- 1080p – Up to 88% faster with Crossfire
- 1440p – Up to 66% faster with Crossfire
- 4K – Only 18% faster with Crossfire
As you can see, multi-GPU setups provide a significant boost at lower resolutions, but have diminishing returns at 4K. The massive workload at higher resolutions makes splitting the frame less efficient. Still, SLI/Crossfire clearly beat even the most powerful single GPUs for HD and 1440p gaming.
Pros of a Multi-GPU Setup
Higher FPS at HD/QHD resolutions
As the benchmarks show, you can get up to 85% better frame rates at 1080p/1440p versus the fastest single GPUs today. This makes high-refresh rate gaming buttery smooth.
Cheaper than top-tier single GPUs
Buying two mid-range cards is often cheaper than flagship GPUs. Two RTX 2070 Supers in SLI provide performance near the RTX 3090 for less money.
Upgrade path
You can start with one card now, and add the second later for an easy performance boost.
Looks awesome
Seeing multiple beastly graphics cards in a rig just looks cool for enthusiasts.
Cons of a Multi-GPU Setup
Diminishing returns at 4K
As shown earlier, multi-GPU scaling drops significantly at higher resolutions. The massive 4K workload makes splitting between cards less efficient.
Not supported in all games
SLI/Crossfire requires explicit support from the game engine. Many new titles do not optimize for multi-GPU, reducing gains.
Microstuttering
Trying to sync frames from multiple GPUs can sometimes cause stuttering, negatively impacting smoothness.
More heat and power draw
Having two cards produces substantially more heat and power consumption versus a single GPU system. Requires robust cooling and PSU.
More expensive motherboards
You need a motherboard with multiple PCIe x16 slots and support for SLI/Crossfire. This bumps up costs.
No ray tracing or DLSS benefit
Nvidia’s RTX features like ray tracing and DLSS do not scale with SLI. A single RTX card is better for leveraging these.
When Does Multi-GPU Make Sense?
Given the tradeoffs, here are examples where a multi-GPU setup shines:
- Playing competitive esports at 1080p with a 240Hz+ monitor
- Powering an ultra-wide 1440p display over 100 Hz
- Building a top-tier rig focused on conventional rasterization performance
And cases where a single powerful GPU may be preferable:
- Gaming at 4K resolution
- Playing games requiring RTX features like ray tracing
- Building in a small form factor case with limited space and cooling
So in summary, if your priority is super high frame rates in HD/QHD, and you have the budget and space, multi-GPU still provides tangible benefits today. But for 4K, ray tracing, or smaller builds, a single GPU is likely the better choice. Consider your own gaming needs and decide – to SLI or not to SLI!
Example Builds
Here are two example high-end builds, one with a single GPU and one with SLI, to illustrate the difference:
Single GPU Build
|Type|Item|Price|
|-|-|-|
|CPU|AMD Ryzen 9 5900X 3.7 GHz 12-Core Processor|$444.99 @ Newegg|
|CPU Cooler|Corsair iCUE H150i ELITE CAPELLIX 75 CFM Liquid CPU Cooler|$189.99 @ Amazon|
|Motherboard|Asus ROG Crosshair VIII Hero (WI-FI) ATX AM4 Motherboard|$379.99 @ Amazon|
|Memory|G.Skill Trident Z RGB 32 GB (2 x 16 GB) DDR4-3600 CL16 Memory|$169.99 @ Newegg|
|Storage|Samsung 970 Evo Plus 1 TB M.2-2280 NVME Solid State Drive|$114.99 @ Adorama|
|Video Card|Asus GeForce RTX 3090 24 GB STRIX GAMING OC Video Card|$1849.00 @ Newegg|
|Case|Lian Li O11D XL-W ATX Full Tower Case|$219.99 @ B&H|
|Power Supply|Corsair RMx (2021) 1000 W 80+ Gold Certified Fully Modular ATX Power Supply|$174.99 @ Amazon|
|Prices include shipping, taxes, rebates, and discounts|||
|Total|$3543.93||
This single GPU build uses the mighty RTX 3090, Ryzen 9 5900X, and 32GB of RAM. It can crush any game at 4K with all the bells and whistles. The 1000W PSU ensures adequate headroom for boosting the 3090.
SLI Build
|Type|Item|Price|
|-|-|-|
|CPU|AMD Ryzen 7 5800X3D 3.4 GHz 8-Core Processor|$449.00 @ Amazon|
|CPU Cooler|ARCTIC Liquid Freezer II 240 56.3 CFM Liquid CPU Cooler|$92.14 @ Amazon|
|Motherboard|Gigabyte X570 AORUS MASTER ATX AM4 Motherboard|$269.99 @ Newegg|
|Memory|G.Skill Trident Z Neo 32 GB (2 x 16 GB) DDR4-3600 CL16 Memory|$149.99 @ Newegg|
|Storage|Western Digital Black SN850 1 TB M.2-2280 NVME Solid State Drive|$119.99 @ Western Digital|
|Storage|Seagate Barracuda Compute 8 TB 3.5″ 5400RPM Internal Hard Drive|$149.99 @ Amazon|
|Video Card|Gigabyte GeForce RTX 3080 Ti 12 GB GAMING OC Video Card|$1049.99 @ Newegg|
|Video Card|Gigabyte GeForce RTX 3080 Ti 12 GB GAMING OC Video Card|$1049.99 @ Newegg|
|Case|Corsair 1000D ATX Full Tower Case|$484.99 @ Amazon|
|Power Supply|Corsair AX 1600 W 80+ Titanium Certified Fully Modular ATX Power Supply|$409.00 @ Amazon|
|Custom|SLI Bridge|[$40.00]|
|Prices include shipping, taxes, rebates, and discounts|||
|Total|$4265.07||
This SLI build uses two RTX 3080 Tis with an AMD Ryzen 7 5800X3D and X570 motherboard. The dual GPUs will crush 1440p and 1080p gaming. The 1600W PSU provides plenty of headroom for the power-hungry cards, and the full tower case offers expansive cooling.
Conclusion
While multi-GPU setups are not as seamless as a single card, they can provide substantial gains in HD and 1440p gaming. But for 4K or ray tracing, a single monstrous GPU usually makes more sense. Consider your own gaming needs, resolution, and budget when deciding between these high-end options. With the right build, both approaches offer awesome PC gaming performance!
