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Convert notes into blockquotes

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James Gregory 2013-12-31 11:06:31 +11:00
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@ -120,9 +120,13 @@ because those instructions that the V-pipe can handle are able to pair
only with certain U-pipe instructions. For example, **MOVSD** uses both
pipes, so no instruction can be executed in parallel with **MOVSD**.
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![](images/i.jpg) *The use of both pipes does make **MOVSD** nearly twice as fast on the Pentium as on the 486, but it's nonetheless slower than using equivalent simpler instructions that allow for superscalar execution. Stick to the Pentium's RISC-like instructions—the pairable instructions I'll discuss next—when you're seeking maximum performance, with just a few exceptions such as **REP MOVS** and **REP STOS**.*
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> ![](images/i.jpg)
> The use of both pipes does make **MOVSD** nearly twice as fast on the
> Pentium as on the 486, but it's nonetheless slower than using equivalent
> simpler instructions that allow for superscalar execution. Stick to the
> Pentium's RISC-like instructions—the pairable instructions I'll discuss
> next—when you're seeking maximum performance, with just a few exceptions
> such as **REP MOVS** and **REP STOS**.
Trickier yet, register contention can shut down the V-pipe on any given
cycle, and Address Generation Interlocks (AGIs) can stall either pipe at