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SLI Scaling: Can Three GeForce GTX 760s Beat Two 780s?

Test System And Benchmarks

Test System Configuration
CPUIntel Core i7-4770K: 3.50 GHz, 8 MB Shared L3 Cache, LGA 1150 Overclocked to 4.5 GHz at 1.20 V
MotherboardASRock Z87 Extreme9/AC, BIOS 1.80, PEX 8747 48-Lane PCIe 3.0 Switch
CPU CoolerThermalright MUX-120 with Zalman ZM-STG1 Paste
RAMG.Skill F3-17600CL9Q-16GBXLD (16 GB) XMP-2200 CAS 11 at DDR3-1600 CAS 9 Defaults
GTX 780 GraphicsNvidia GeForce GTX 780: 863-902 MHz GPU, 3 GB GDDR5-6008
GTX 760 GraphicsEVGA 04G-P4-2766-KR: 980-1033 MHz GPU, 4 GB GDDR5-6008
Hard DriveSamsung 840 Series MZ-7PD256, 256 GB SSD
SoundIntegrated HD Audio
NetworkIntegrated Gigabit Networking
PowerCorsair AX860i: ATX12V v2.3, EPS12V, 80 PLUS Platinum
System Software
OSMicrosoft Windows 8 Professional RTM x64
GraphicsNvidia GeForce 331.58 WHQL
ChipsetIntel INF

The biggest issue we face when it comes to testing three-way SLI is that Intel’s fastest mainstream CPUs only have 16 PCIe 3.0 lanes. The LGA 2011 platform is an alternative, though the processor architecture it hosts is one generation older. The other alternative is to use a motherboard with a bridge chip able to turn 16 lanes of PCI Express connectivity into 32. ASRock sent over our lab's first Z87-based platform with the requisite on-board components, its Z87 Extreme9/AC.

The reason bridges work so well is that they’re able to send multiple copies of the same data to each card. Because the members of an SLI array operate on identical information, this has the benefit of multiplying out bandwidth without needing a much more complicated on-die PCI Express controller. A slightly latency penalty is the only noticeable drawback to this approach, since data has to go through one more piece of silicon.

Battlefield 3Campaign Mode, "Going Hunting" 90-Second Fraps Test Set 1: Medium Quality Defaults (No AA, 4x AF) Test Set 2: Ultra Quality Defaults (4x AA, 16x AF)
Far Cry 3V. 1.05, DirectX 11, 50-Second Fraps "Amanaki Outpost" Test Set 1: High Quality, No AA, Standard ATC, SSAO Test Set 2: Ultra Quality, 4x MSAA, Enhanced ATC, HDAO
F1 2012Steam version, in-game benchmark Test Set 1: High Quality Preset, No AA Test Set 2: Ultra Quality Preset, 8x AA
Metro: Last LightSteam version, Built-In Benchmark, "Frontline" SceneTest Set 1: DX11, Med Quality, 4x AF, Low Blur, No SSAA, No Tesselation, No PhysXTest Set 2: DX11, High Quality, 16x AF, Normal Blur, SSAA, Tesselation Normal, No PhysX
Tomb RaiderSteam version, Built-In Benchmark Test Set 1: High Quality Preset (8x AF, FXAA), Motion Blur, Screen Effects Test Set 2: Ultimate Quality, (16x AF,  FXAA), Tesselation, TressFX
Synthetic Benchmarks
3DMark ProfessionalVersion 1.1, SystemInfo, Fire Strike Benchmark (Extreme Off/On)
Thomas Soderstrom
Thomas Soderstrom is a Senior Staff Editor at Tom's Hardware US. He tests and reviews cases, cooling, memory and motherboards.