Voodoo2
The Voodoo2 (or Voodoo2) was a set of three specialized 3D graphics chips on a single chipset setup, made by 3dfx. It was released in February 1998 as a replacement for the original Voodoo Graphics chipset. The card ran at a chipset clock rate of 90 MHz and used 100 MHz EDO DRAM, and was available for the PCI interface. The Voodoo2 came in two models, one with 8 MB RAM and one with 12 MB RAM. The 8 MB card had 2 MB of memory per texture mapping unit (TMU) vs. 4 MB on the 12 MB model. The 4 MB framebuffer on both cards supported a maximum screen resolution of 800 × 600, while the increased texture memory on the 12 MB card allowed more detailed textures. Some boards with 8 MB could be upgraded to 12 MB with an additional daughter board. Each of the three chips present on the card had its own 64-bit RAM interface, giving the card a "total" bus width of 192 bits. The Voodoo2 had an increased chip-count compared to the original two-chip Voodoo card. Competing products such as the ATI Rage Pro, NVIDIA RIVA 128, and Rendition Verite 2x00 were single-chip products, each with integrated 2D GUI/VGA accelerators. As with the original Voodoo, the Voodoo2 was a dedicated 3D accelerator, and had to be used in conjunction with a conventional 2D graphics card. It required the same external pass-through cabling familiar to owners of the Voodoo.
The Voodoo2's third chip was a second TMU that allowed a second texture to be drawn during the same graphics engine pass, and thus with no performance penalty. At time of introduction, Voodoo2 was the only 3D card capable of single-cycle dual-texturing. Usage of the Voodoo2's second TMU depended on application software; Quake II and Unreal exploited dual-texturing to great effect. In games that did not use more than one texture layer, Voodoo2 was only faster than Voodoo1 because of its higher clock speed.
The Voodoo2 introduced Scan-Line Interleave (SLI) capability to the consumer PC market. In SLI mode, two Voodoo2 boards were installed in a PC and ran in parallel, with each unit drawing half the lines of the display. Voodoo2 SLI not only doubled rendering throughput, it also increased the total framebuffer memory, and thus the maximum supported screen resolution increased to a then-impressive 1024 × 768. However, texture memory was not doubled because each card needed to duplicate the scene data. The original Voodoo Graphics also had SLI capability, but it was only used in the arcade and professional markets.
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