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3DNow and Enhanced 3DNow

3DNow technology is AMD's alternative to the SSE instructions in the Intel processors. Actually 3DNow originally came out in the K6 series before Intel released SSE in the Pentium III, and then AMD added Enhanced 3DNow to the Athlon and Duron processors. AMD licensed MMX from Intel and all its K6 series, Athlon, Duron, and later processors include full MMX instruction support. Not wanting to additionally license the SSE instructions being developed by Intel, AMD first came up with a different set of extensions beyond MMX called 3DNow. Introduced in May 1998 in the K6-2 processor and later enhanced when the Athlon was introduced in June 1999, 3DNow and Enhanced 3DNow are sets of instructions that extend the multimedia capabilities of the AMD chips beyond MMX. This allows greater performance for 3D graphics, multimedia, and other floating-point-intensive PC applications.

3DNow technology is a set of 21 instructions that uses SIMD (Single Instruction Multiple Data) techniques to operate on arrays of data rather than single elements. Enhanced 3DNow adds 24 more instructions to the original 21 for a total of 45 new instructions. Positioned as an extension to MMX technology, 3DNow is similar to the SSE (streaming SIMD extensions) found in the Pentium III and Celeron processors from Intel. According to AMD, 3DNow provides approximately the same level of improvement to MMX as did SSE, but in fewer instructions with less complexity. Although similar in capability, they are not compatible at the instruction level so that software specifically written to support SSE will not support 3DNow, and vice versa.

Just as with SSE, 3DNow also supports single precision floating point SIMD (Single Instruction Multiple Data) operations and enables up to four floating point operations per cycle. 3DNow floating point instructions can be mixed with MMX instructions with no performance penalties. 3DNow also supports data prefetching.

Also like SSE, 3DNow is well supported by software including Microsoft Windows 9x, Windows NT 4.0, and all newer Microsoft operating systems. Application programming interfaces such as Microsoft's DirectX 6.x API and SGI's Open GL API have been optimized for 3DNow technology, as have the drivers for many leading 3D graphic accelerator suppliers, including 3Dfx, ATI, Matrox, and nVidia. While many games and video drivers support 3DNow, support is lacking from some of the major business graphics applications like Adobe Photoshop.

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