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Intel Crestmont: The Next-Gen E-Cores

6/02/2024
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Let's dive into the fascinating world of Intel Crestmont. 🚀

Intel Crestmont: The Next-Gen E-Cores

Intel Crestmont is a significant architectural leap in the realm of E-Cores, which play a crucial role in Intel's consumer CPU strategy. Let's explore the key aspects of Crestmont:

  1. Background and Context:

    • Crestmont is the successor to the Gracemont architecture, which was used in Intel's Alder Lake and Raptor Lake processors.
    • It's part of Intel's 14th Gen Meteor Lake CPUs, specifically designed for mobile devices.

  2. Architecture Overview:

    • Crestmont is a 6-wide, superscalar, out-of-order core.
    • It features enhancements throughout the pipeline, making it more efficient than its predecessor.
    • Comparable in width to high-performance cores from both Intel and AMD, Crestmont aims to strike a balance between performance and power efficiency.

  3. E-Cores and LPE-Cores:

    • Meteor Lake doubles down on E-Cores, and Crestmont is at the heart of this strategy.
    • LPE-Cores (Low Power E-Cores) are a new addition. They use the same Crestmont architecture but focus on low-power compute rather than raw performance.
    • LPE-Cores are ideal for handling light tasks without significantly impacting overall power consumption.

  4. System Architecture:

    • In a typical Meteor Lake SoC, Crestmont E-Cores are arranged in two quad-core clusters.
    • These E-Core clusters interface with the ring bus, allowing them to share an L3 cache with the P-Cores.
    • Additionally, there's a separate cluster for LPE-Cores, which don't share the CPU's L3 cache but provide energy-efficient processing capabilities.

  5. Clock Behavior:

    • Crestmont's boost scheme is somewhat dated, with fixed multi-core boost ratios based on active core count.
    • Loading more than four Crestmont cores drops the frequency to 3.1 GHz, and further decreases to 2.8 GHz if more than six cores are in use.
    • However, the P-Cores (Redwood Cove) use a modern boost scheme and can clock independently of the E-Cores.

  6. IPC Gain and Improvements:

    • Crestmont achieves a double-digit IPC gain over Gracemont (its predecessor).
    • This improvement is attributed to several factors:
      • Enhanced branch prediction unit
      • Broader 9-wide decode unit (compared to 6-wide in Gracemont)
      • 8-wide integer ALU (compared to 4 in Gracemont)
      • Dependency optimization in the out-of-order engine
      • Deeper queuing across the engine.

In summary, Intel Crestmont represents a step forward in E-Core architecture, balancing performance and efficiency. As we await the arrival of Meteor Lake processors, Crestmont's innovations promise exciting possibilities for mobile computing. 🌟