Re: NOP instruction

Tigran Aivazian (tigran@aivazian.demon.co.uk)
Tue, 15 Dec 1998 11:47:01 +0000 (GMT)

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On Tue, 15 Dec 1998, Gabriel Paubert wrote:
> Actually the Intel nop is coded as xchg [e]ax,[e]ax since the 8088. On the
> 386, it took exactly the same time as xchg [e]ax with any other register
> and was slow. From the 486 or Pentium, I can't remember, the NOP is
> optimized and much faster than the actual xchg instructions.
Besides xchg is atomic (which is why it is used in locking primitives (at least
on some systems)) and is to be avoided whenever possible.

Regards,
Tigran.

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