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INSTRUCTION SET REFERENCE
OUTS/OUTSB/OUTSW/OUTSDOutput String to Port (Continued)
The OUTS, OUTSB, OUTSW, and OUTSD instructions can be preceded by the REP prefix for
block input of ECX bytes, words, or doublewords. Refer to REP/REPE/REPZ/REPNE
/REPNZRepeat String Operation Prefix in this chapter for a description of the REP prefix.
This instruction is only useful for accessing I/O ports located in the processors I/O address
space. Refer to Chapter 10, Input/Output of the Intel Architecture Software Developers Manual,
Volume 1, for more information on accessing I/O ports in the I/O address space.
Intel Architecture Compatibility
After executing an OUTS, OUTSB, OUTSW, or OUTSD instruction, the Pentium
®
processor
insures that the EWBE# pin has been sampled active before it begins to execute the next instruc-
tion. (Note that the instruction can be prefetched if EWBE# is not active, but it will not be
executed until the EWBE# pin is sampled active.) Only the P6 family of processors has the
EWBE# pin. For the P6 family processors, upon execution of an OUTS, OUTSB, OUTSW, or
OUTSD instruction, the P6 family of processor will not execute the next instruction until the
data phase of the transaction is complete.
