Hardware Requirements, Continued
The Connector: According to current information, the connectors are standardized and will be available from a number of card manufacturers. As a result, buyers will be able to upgrade to SLI at any later date by simply buying a second card and the connector board.
The connector on GF 6800 PCI Express cards.
The SLI connector PCB sticks two cards together.
Mix-and-Match: As long as both cards are of the same type (i.e. 2x GF 6800 GT, for example) you should be able to mix cards from different manufacturers. In such a case, card A is from company X while card B is from company Y. Nonetheless, NVIDIA recommends buying both cards from the same company. Whether this mix-and-match method will actually work out in practice remains to be seen, as boards of the same type from different companies are often outwardly identical but may use different memory timings or clock speeds.
SLI via Dual-GPU Board: Looking at this development, the question arises why NVIDIA didn't simply put two graphics processors on one board to begin with. One problem with this concept is the PCI Express bus, which isn't really a bus at all but a point-to-point connection. To be able to use two graphics processors, you would need to use some sort of bridge or logic to distribute the signals on the card. Additionally, greater size of such a card and the heat problems associated with a dual-chip setup would also need to be solved somehow. Lastly, one of the strongest arguments in favor of SLI is the option of upgrading at any time.