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Encyclopedia > 3DNow!
The first 3DNow! CPU
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The first 3DNow! CPU

3DNow! is the name of a multimedia extension created by AMD for its processors, starting with the K6-2 in 1998. In more technical terms, it's an addition of SIMD instructions to the traditional x86 instruction set, to better cope with the vector-processing requirements of many graphic-intensive applications. It was originally developed as an enhancement to the MMX instruction set to extend it from integer-only to floating point capabilities too. Later, Intel would add similar (but incompatible) instructions to the Pentium III, known as SSE. Image File history File links AMDK6-2_3dnow. ... Image File history File links AMDK6-2_3dnow. ... Advanced Micro Devices, Inc. ... The K6-2 was a x86 microprocessor manufactured by AMD, available in speeds ranging from 266 to 550 MHz. ... -1... x86 or 80x86 is the generic name of a microprocessor architecture first developed and manufactured by Intel. ... An instruction set, or instruction set architecture (ISA), describes the aspects of a computer architecture visible to a programmer, including the native datatypes, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O (if any). ... MMX is a SIMD instruction set designed by Intel, introduced in their Pentium MMX microprocessors. ... Pentium III logo The Pentium III is an x86 (more precisely, an i686) architecture microprocessor by Intel, introduced on February 26, 1999. ... SSE (Streaming SIMD Extensions) is a SIMD (Single Instruction, Multiple Data) instruction set designed by Intel, and introduced in 1999 in their Pentium III series processors as a reply to AMDs 3DNow! (which had debuted a year earlier). ...


AMD upgraded the instruction set over time. The first enhancement was called quite simply Enhanced 3DNow!, introduced with the first-generation Athlons; which added about 19 new instructions mostly to do with instruction prefetching, etc. The second enhancement was called 3DNow! Professional, which was introduced with the Athlon XP processors; this version basically integrated the full SSE1 technology from Intel and combined it with its own 3DNow!. Athlon is the brand name applied to a series of different x86 processors designed and manufactured by AMD. The original Athlon, or Athlon Classic, was the first seventh-generation x86 processor and, in a first, retained the initial performance lead it had over Intels competing processors for a significant... SSE (Streaming SIMD Extensions) is a SIMD instruction set designed by Intel, and introduced in their Pentium III series processors as a reply to AMDs 3DNow!, which had debuted a year or so earlier. ...


One advantage of 3DNow! is that it is possible to add or multiply the two numbers that are stored in the same register. With SSE, each number can only be combined with a number in the same position in another register. This capability, known as horizontal in Intel-speak, is the major addition to the SSE3 instruction set, recently released. SSE3, also known by its Intel code name Prescott New Instructions (PNI), is the third iteration of the SSE instruction set for the IA-32 architecture. ...


A disadvantage with 3DNow! compared to SSE is that it only stores two numbers in a register, as opposed to four in SSE. However, 3DNow! instructions can generally be executed with a lower latency and throughput than SSE instructions.


3DNow! also shares the same physical registers as MMX, while SSE has its own independent registers. Because these MMX and 3DNow! registers are also used by the standard x87 FPU, 3DNow! instructions and x87 instructions can't be executed simultaneously. However, since it is aliased to the x87 FPU, the 3DNow! & MMX register states can be saved and restored by the traditional x87 FNSAVE and FRSTR instructions. Using the traditional x87 instructions meant that no operating system modifications had to be made to support 3DNow!. In computing, an operating system (aka, OS) is the system software responsible for the direct control and management of hardware and basic system operations. ...


By contrast, to save and restore the state of SSE registers required the use of the newly added FXSAVE and FXRSTR instructions; the FX* instructions are an upgrade to the older x87 save and restore instructions because these could save not only SSE register states but also those x87 register states (hence which meant that it could save MMX and 3DNow! registers too). Use of the FX* instructions required that the processor entered a slightly modified version of Protected mode called Enhanced mode; the only difference between Protected mode and Enhanced mode was that the latter enabled the use of SSE (and thus the FX* instructions), and the former disabled their use. Operating systems which supported SSE would enter Enhanced mode, whereas those which were unaware of its existence would enter only traditional Protected mode. Protected mode (sometimes abbreviated p-mode) is an operational mode of x86-compatible CPUs of the 80286 series or later. ... In computing, an operating system (OS) is the system software responsible for the direct control and management of hardware and basic system operations. ...


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