Instruction Set (Continued)
9.6 NATIONAL SEMICONDUCTOR EXTENDED MMX INSTRUCTION SET
National Semiconductor has added instructions to its
implementation of the MMX Architecture in order to facili-
tate writing of multimedia applications. In general, these
instructions allow more efficient implementation of multi-
media algorithms, or more precision in computation than
can be achieved using the basic set of MMX instructions.
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 9-32. Extend MMX Instruction Set Table
Legend
Abbreviation
Description
<----
Result written
[11 mm reg]
mm
Binary or binary groups of digits
One of eight 64-bit MMX registers
A general purpose register
reg
<--sat--
If required, the resultant data is saturated
to remain in the associated data range
<--move--
[byte]
Source data is moved to result location
Eight 8-bit bytes are processed in parallel
Table 9-33 on page 235 summarizes the Extended MMX
Instructions. The abbreviations used in the table are listed
in Table 9-32.
[word]
Four 16-bit WORD are processed in paral-
lel
Configuration control register CCR7(0) at location EBh
must be set to allow the execution of the Extended MMX
instructions.
[dword]
Two 32-bit DWORDs are processed in par-
allel
[qword]
One 64-bit QWORD is processed
[sign xxx]
The BYTE, WORD, DWORD or QWORD
most significant bit is a sign bit
mm1, mm2
mod r/m
MMX Register 1, MMX Register 2
Mod and r/m byte encoding (page 6-6 of
this manual)
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 four
WORDs in destination register.
packwb
Pack four WORDs from source and four
WORDs from destination into eight BYTEs
in destination register.
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