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Scan-Line Interleave

Voodoo2 with SLI cable at top left
Manufacturer	3DFX
Type	Multi-GPU technology
Released	1998
Connectivity	Ribbon cable
Successor	Scalable Link Interface

Scan-Line Interleave (SLI) is a multi-GPU method developed by 3DFX for linking two (or more) video cards or chips together to produce a single output. It is an application of parallel processing for computer graphics, meant to increase the processing power available for graphics.^[1][2]

3DFX's SLI technology was first introduced in 1998 with the Voodoo2 line of graphics accelerators. The original Voodoo Graphics card and the VSA-100^[3][4] were also SLI-capable. However, in the case of the former, it was only used in arcades,^[5][6] as well as professional applications via Primary Image's Piranha^[7][8][9] card, intended for use with simulations using various^[10][11] graphics APIs such as OpenGL, Glide, or Primary Image's own Tempest API. Support for the MultiGen OpenFlight Format in particular was specifically advertised.^[7][10][11]

NVIDIA reintroduced the SLI initialism in 2004 as Scalable Link Interface. NVIDIA's SLI, compared to 3DFX's SLI, is modernized to use graphics cards interfaced over the PCI Express bus.^[12]

3DFX's SLI design was the first attempt, in the consumer PC market, at combining the rendering power of two video cards. The two 3DFX cards were connected by a small ribbon cable inside the PC. This cable shared graphics and synchronization information between the cards. Each 3DFX card rendered alternating horizontal lines of pixels composing a frame.^[1][2]

• AMD CrossFireX

• The 3dfx Help Page