SSE For Athlon 4 - 3DNow! Professional
In February 1999 Intel launched Pentium III with the 'Katmai'-core. The only significant improvement over its predecessor 'Pentium II' was the addition of 70 new instructions that Intel called 'SSE' = 'Streaming SIMD Extensions'. These extensions were supposed to accelerate multimedia and 3D-applications, but a part of SSE were also the 'streaming' instructions, including several data pre-fetch operations.
AMD's pendant was first '3DNow!' of K6-2 and K6-3 and later the 'Enhanced 3DNow!' of Athlon. These AMD-specific SIMD-instructions proved pretty much just as powerful as Intel's SSE, but AMD continued to have a rather hard time to make software developers implement code with those instructions. Due to Intel's influence in the business and the big success of Pentium III, the implementation of SSE in current software is much more common than 3DNow!-support.
18 of the 'Enhanced 3DNow!-instructions are identical to Intel's SSE-stuff for a long time. Now AMD added the remaining 52 instructions as well as the status bit that is probed by software that wants to know if the system processor supports SSE. This means that Athlon 4 basically 'understands' all SSE-code and is therefore able to take advantage of software that was SSE-optimized. The fact that AMD is finally following Intel's lead can be seen as the first step towards AMD's future 'Hammer'-line of processors, which are supposed to come with a full 'SSE2'-implementation. Those are the 144 double precision floating point SIMD instructions introduced by Intel's Pentium 4 processor last year.
Don't expect any major performance advantage from Athlon 4's SSE-capabilities. Firstly we don't know how well those instructions were implemented and how many clock cycles those instructions actually require. Secondly are we still waiting for a proper proof that SSE is particularly beneficial altogether. I think that AMD is simply willing to finally leave 3DNow! behind and focus on the pure implementation of Intel's multimedia extensions only.