Specifications

Computer Architecture and Maintenance (G-Scheme-2014)
that the cache has the correct data 90% of the time, and consequently the processor
runs at full speed (233 MHz in this example) 90% of the time. However, 10% of the time
the cache controller guesses incorrectly, and the data has to be retrieved out of the
significantly slower main memory, meaning the processor has to wait. This essentially
throttles the system back to RAM speed, which in this example was 60 ns or 16 MHz.
In this analogy, the processor was 14 times faster than the main memory. Memory
speeds have increased from 16 MHz (60 ns) to 333 MHz (3.0 ns) or faster in the latest
systems, but processor speeds have also risen to 3 GHz and beyond. So even in the
latest systems, memory is still 7.5 or more times slower than the processor. Cache is
what makes up the difference.
The main feature of L1 cache is that it has always been integrated into the
processor core, where it runs at the same speed as the core. This, combined with the hit
ratio of 90% or greater, makes L1 cache important for system performance.
Level 2 Cache
In an actual Pentium class (Socket 7) system, the L2 cache is mounted on
the motherboard, which means it runs at motherboard speed (66 MHz, or 15 ns in this
example).
All modern processors have integrated L2 cache that runs at the same speed as the
processor core, which is also the same speed as the L1 cache. The screenshot below
illustrates the cache types and sizes in the AMD A10-5800Kprocessor, as reported by
CPU-Z.
The AMD A10-
5800K processor is a quad-
core processor with L1 and
L2 cache.
Level 3 Cache
Most late-model mid-range
and high-performance
processors also contain a
third level of cache known
as L3 cache. In the past,
relatively few processors
had L3 cache, but it is
becoming more and more
common in newer and
Prepared By – Prof. Manoj.kavedia (9860174297 – 9324258878 ) (www.kavediasir.yolasite.com)
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