The information seen on both SLI and Crossfire states the need for identical cards to be insync. But you have to have the same manufacturer's chipset on the board. Other setups simply using two video cards for multi monitor setups have worked. But those have been with a PCI card added to the existing AGP or PCI-E model when made to work. For SLI requirements BFG has a good note to read.
SLI Requirements
>>Combine multiple BFG NVIDIA GeForce-based graphics cards with an NVIDIA nForce® SLI-based motherboard. IMPORTANT: Graphics cards MUST be from the same manufacturer and contain identical GPUs. For example, a BFG GeForce 7900 GTX OC PCI-E can only be paired with another BFG GeForce 7900 GTX OC PCI-E graphics card.>>Plug Your BFG Tech SLI-ready graphics card into an SLI-ready PCI Express motherboard. IMPORTANT: The motherboard MUST support two physical connectors that are capable of having two NVIDIA SLI-based PCI Express graphics cards plugged into them.>>Connect both graphics cards using the NVIDIA SLI connector.>>Download the latest NVIDIA ForceWare™ unified driver with SLI support from
www.nvidia.com>>For the latest information and more techical details on SLI visit
www.nvidia.com/slihttp://www.bfgtech.com/7900GTX_512_PCIX.html
For running two ATI X1900 series cards the following explains what is needed there.
Crossfire Explanation and typical requirements!
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If installing two X1900 series cards each card will require it's own connection to your power supply not just power from the motherboard x16 slot that's required for each!
You will need a good Crossfire motherboard!
Note on Crossfire Motherboards: There are several but all but one are based on Xpress 200, which means that when 2 cards are used the x16 slots will run at x8 speed in Crossfire! There is one 939 socket motherboard which was released March 1st that has Xpress 3200, which allows both x16 slots to run at x16 speed even in Crossfire!
However! For Intel users the Crossfire Benchmarks have shown there is almost no increase in graphic speeds with Xpress 3200.
The boxes will say a 550 watt power supply for dual cards but to work best they will need a very good 600 watt or higher Dual Rail power supply
The critical requirement again is that your power supply ideally has a total of 38 amps on dual 12v rails (this assumes a fully loaded system)
For example your power supply might say 20 amps on 12v1 and 18 amps on 12v2 (dual rails required)
Each X1900 series Card will require its own 6 pin power connector, which is why you require a dual rail power supply These power supplies are found easiest by looking for SLI ready power supplies, But since ATI X1900 cards produce better
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