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Revision 1.0

Instruction Set (Continued)

8.6

EXTENDED MMX INSTRUCTION SET

National Semiconductor has added instructions to its

implementation of the Intel MMX architecture in order to

facilitate writing of multimedia applications. In general,

these instructions allow more efficient implementation of

multimedia algorithms, or more precision in computation

than can be achieved using the basic set of MMX instruc-

tions. All of the added instructions follow the SIMD (single

instruction, multiple data) format. Many of the instructions

add flexibility to the MMX architecture by allowing both

source operands of an instruction to be preserved, while

the result goes to a separate register that is derived from

the input.

Table 8-33 summarizes the Extended MMX Instructions.

Theabbreviationsusedin the tableare listed in Table8-32.

Configuration control register CCR7(0) at Index EBh (see

Table 3-11 on Page 53) must be set to allow the execution

of the Extended MMX instructions.

Table 8-32. Extend MMX Instruction Set

Table Legend

Abbreviation

Description

<----

Result written.

[11 mm reg]

Binary or binary groups of digits.

One of eight 64-bit MMX registers.

reg

A general purpose register.

<--sat--

If required, the resultant data is saturated to

remain in the associated data range.

<--move--

Source data is moved to result location.

[byte]

Eight 8-bit BYTEs are processed in parallel.

[word]

Four 16-bit WORDs are processed in

parallel.

[dword]

Two 32-bit DWORDs are processed in

parallel.

[qword]

One 64-bit QWORD is processed.

[sign xxx]

The BYTE, WORD, DWORD or QWORD

most significant bit is a sign bit.

mm1, mm2

MMX Register 1, MMX Register 2.

mod r/m

Mod and r/m byte encoding (Table 8-15 on

page 217).

pack

Source data is truncated or saturated to

next smaller data size, then concatenated.

packdw

Pack two DWORDs from source and two

DWORDs from destination into QWORDs in

destination register.

packwb

Pack QWORDs from source and QWORDs

from destination into eight BYTEs in desti-

nation register.

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