Linking Graphics Cards
Some graphics cards can be linked together to allow scaling of the graphics processing across multiple cards. This is done using either the PCIe bus on the motherboard, or, more commonly, a data bridge www.graphicscardsadvisor.com. Generally, the cards must be of the same model to be linked, and most low power cards are not able to be linked in this way. AMD and Nvidia both have proprietary methods of scaling, CrossFireX for AMD, and SLI (since the Turing generation, renamed to NVLink) for Nvidia. Cards from different chipset manufacturers, architectures cannot be used together for multi card scaling. If a graphics card has different sizes of memory, the lowest value will be used, with the higher values being disregarded. Currently, scaling on consumer grade cards can be done using up to four cards. The use of four cards requires a large motherboard with a proper configuration. Nvidia’s GeForce GTX 590 video card has the ability to be configured in this four card configuration. As stated above, users will want to stick to the same performance card for optimal use. Motherboards like ASUS Maximus 3 Extreme and Gigabyte GA EX58 Extreme are certified to work with this configuration. For proper performance of your 4 card configuration, it’s recommend to use a core i7 CPU with turbo boost to avoid the bottleneck throughput. A certificated large power supply is necessary to run the cards in SLI or CrossFireX. Power demands must be known before a proper supply is installed. For the four card configuration, a 1000+ watt supply is needed. AcBel PC8055-000G and Corsair AX1200 supplies are examples. With any powerful video card like a GTX 1060+ or 1080, thermal management can be overlooked. Video cards require a well vented chassis and thermal solution. Water or air cooling are required for all video cards, with larger configurations needing water solutions to achieve proper performance.
As the processing power of video cards has increased, so has their demand for electrical power. Current high-performance video cards tend to consume a great deal of power. For example, the thermal design power (TDP) for the GeForce GTX TITAN is 250 Watts. When tested while gaming, the GeForce GTX 1080 Ti Fe averaged 227 Watts of power consumption. While CPU and power supply makers have recently moved toward higher efficiency, power demands of GPUs have continued to rise, so video cards may have the largest power consumption in a computer. Although power supplies are increasing their power too, the bottleneck is due to the PCI-Express connection, which is limited to supplying 75 Watts. Modern video cards with a power consumption of over 75 Watts usually include a combination of six-pin (75 W) or eight-pin (150 W) sockets that connect directly to the power supply. Providing adequate cooling becomes a challenge in such computers. Computers with multiple video cards may need power supplies in the 1000–1500 W range. Heat extraction becomes a major design consideration for computers with two or more high-end video cards.
Video cards for desktop computers come in one of two size profiles, which can allow a graphics card to be added even to small-sized PCs. Some video cards are not of usual size, and are thus categorized as being low profile. Video card profiles are based on width only, with low-profile cards taking up less than the width of a PCIe slot. Length and thickness can vary greatly, with high-end cards usually occupying two or three expansion slots, and with dual-GPU cards -such as the Nvidia GeForce GTX 690- generally exceeding 250 mm (10 in) in length. Generally, most users will prefer a lower profile card if the intention is to fit multiple cards or they run into clearance issues with other motherboard components like the DIMM or PCIE slots. This can be fixed with a larger case that comes in sizes like mid tower and full tower. Full towers can usually fit larger motherboards in sizes like ATX and micro ATX. The larger the case, the larger the motherboard, the larger the graphics card or multiple other components that will acquire case real-estate.
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