PCIe Lanes - PCIe 8x vs 16x in SLI

The video opens by contrasting two high-end Intel CPUs, the 5820K and 5930K, highlighting a surprising difference in PCIe lane counts despite only a small clock speed gap and price disparity. The host explains that the 5820K provides 28 PCIe Gen 3 lanes, while the 5930K offers 40 lanes, which serves as the foundational premise for evaluating multi-GPU configurations in SLI. A thorough primer on PCIe lanes follows, including how bus width (x1, x4, x8, x16) translates into usable bandwidth and how different card and motherboard slot combinations interoperate. The host emphasizes that a card can operate at the speed of the lowest link in the chain when lanes are insufficient, setting up the core question: does higher lane count meaningfully impact real-world gaming performance when running multiple GTX 980 GPUs in SLI? The discussion then covers how PCIe generations impact throughput, noting that Gen 3 can be significantly faster than older generations and that an 8x link on a Gen 3 system can behave similarly to other combinations under certain conditions. The test bed is laid out in detail, with four GTX 980 GPUs, a Gigabyte X99 Gaming 5 board, 16 GB of DDR4, and a 1500W power supply, all running at a conservative overclock. The results section explains the testing methodology, including 4K gaming with demanding settings and the use of FRAPS for average frame rates across multiple benchmarks, with particular attention to 2-way, 3-way, and 4-way SLI configurations and how lane distribution affects perceived performance. The video concludes with practical recommendations: for gamers, 2- or 3-GPU setups remain the most sensible per-frame improvements, while 4-way SLI offers diminishing returns and is constrained by CPU lane limits on 28-lane CPUs, though AMD configurations can sometimes bypass some of these limitations. The host also advises checking motherboard manuals before upgrading to ensure PCIe resources like M.2, SATA Express, or USB 3 headers remain available when multiple PCIe cards are installed, and encourages viewers to engage with the community forums for guidance. Overall, the video aims to clarify common misconceptions about PCIe lane counts, offering concrete data and actionable guidance for enthusiasts considering multi-GPU builds on X99 platforms versus mainstream chipsets.

Topics · computer hardware · pcie · gaming · performance