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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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19-02.md
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@ -10,9 +10,11 @@ chapter: '19'
pages: 373-375
---
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![](images/i.jpg) *The Pentium, on the other hand, has two separate 8K caches, one for code and one for data, so code prefetches can never collide with data fetches; the prefetch queue can stall only when the code being fetched isn't in the internal code cache.*
------------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> ![](images/i.jpg)
> The Pentium, on the other hand, has two separate 8K caches, one for code
> and one for data, so code prefetches can never collide with data
> fetches; the prefetch queue can stall only when the code being fetched
> isn't in the internal code cache.
(And yes, self-modifying code still works; as with all Pentium changes,
the dual caches introduce no incompatibilities with 386/486 code.) Also,
@ -40,9 +42,12 @@ bits, and runs twice as fast, at 66 MHz, so the Pentium can fetch both
instruction and data bytes from the external cache four times as fast as
the 486.
------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
![](images/i.jpg) *Even when the Pentium is running flat-out with both pipes in use, it can generally consume only about twice as many bytes as the 486; so the ratio of external memory bandwidth to processing power is much improved, although real-world performance is heavily dependent on the size and speed of the external cache.*
------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> ![](images/i.jpg)
> Even when the Pentium is running flat-out with both pipes in use, it can
> generally consume only about twice as many bytes as the 486; so the
> ratio of external memory bandwidth to processing power is much improved,
> although real-world performance is heavily dependent on the size and
> speed of the external cache.
The upshot of all this is that at the same clock speed, with code and
data that are mostly in the internal caches, the Pentium maxes out