Hardware Reference
In-Depth Information
considered mobile processors only, they are not covered here.
The Core 2 was released as a dual-core processor, but since then quad-core versions have also been
released. The dual-core versions of the Core 2 processors have 291 million transistors, whereas the
quad-core versions have double that, or 582 million. They include 1MB or 2MB of L2 cache per
core, with up to 8MB total L2 in the quad-core versions. Initially, all were built on 300mm wafers
using a 65nm process, but since then 45nm versions have been released as well.
The highlights of the Core microarchitecture include the following:
Wide dynamic execution —Internal execution cores that are 33% wider than in previous
generations, allowing each core to execute up to four full instructions simultaneously. Further
efficiencies are achieved through more accurate branch prediction, deeper instruction buffers
for greater execution flexibility, and additional features to reduce execution time.
Intelligent power capability —An advanced power-gating capability that turns on individual
processor subsystems only if they are needed.
Advanced smart cache —A multicore optimized cache that increases the probability that each
execution core can access data from a shared L2 cache.
Smart memory access —Includes a capability called memory disambiguation, which increases
the efficiency of out-of-order processing by providing the execution cores with the intelligence
to speculatively load data for instructions that are about to execute.
Advanced digital media boost —Improves performance when executing Streaming SIMD
Extension (SSE) instructions by enabling 128-bit instructions to be executed at a throughput rate
of one per clock cycle. This effectively doubles the speed of execution for these instructions
compared to previous generations.
The Core 2 family includes both dual-core and quad-core processors under five different names:
Core 2 Duo —Standard dual-core processors
Celeron —Ultra-Low-end single or dual-core processors
Pentium —Low-end dual-core processors (faster than Celeron with larger cache)
Core 2 Quad —Standard quad-core processors
Core 2 Extreme —High-end versions of either dual-core or quad-core processors
Figure 3.34 shows a cutaway view of a Core 2 Duo chip, revealing the single dual-core die
underneath the heat spreader.
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