Extended MMX, also known as EMMI (Extended Multi-Media Instructions), was an instruction set developed by Cyrix

Cyrix

Cyrix Corporation was a microprocessor developer that was founded in 1988 in Richardson, Texas as a specialist supplier of high-performance math coprocessors for 286 and 386 microprocessors. The company was founded by former Texas Instruments staff members and had a long but troubled relationship...

 and implemented on their 6x86 MX and MII line of processors. It extended the MMX instruction set with 12 new instructions useful in multimedia applications. The extensions were not enabled by default, requiring the BIOS or software to enable them. EMMI was never given much support from software developers or acknowledged by Cyrix's competitors (certain Intel SSE

Streaming SIMD Extensions

In computing, Streaming SIMD Extensions is a SIMD instruction set extension to the x86 architecture, designed by Intel and introduced in 1999 in their Pentium III series processors as a reply to AMD's 3DNow! . SSE contains 70 new instructions, most of which work on single precision floating point...

instructions even share opcodes with EMMI instructions). It was never implemented in any processors after the MII.

The EMMI instruction set included:

• paddsiw
• paveb
• pdistib
• pmachriw
• pmagw
• pmulhrw
• pmulhriw
• pmvzb
• pmvnzb
• pmvlzb
• pmvgezb
• psubsiw