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Broadwell µarch

General Info

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Broadwell (BDW) is Intel's microarchitecture based on the 14 nm process for mobile, desktops, and servers. Introduced in early 2015, Broadwell is a process shrink of Haswell which introduced several enhancements.

Codenames

Core	Target
Broadwell Y (BDW-Y)	Core M family, SoC for Smartphones, 2-in-1s Tablets, and notebooks
Broadwell U (BDW-U)	Core ultrabooks
Broadwell H (BDW-H)	IoT (QM87, HM86/HM87 Chipsets), All-in-ones
Broadwell DT (BDW-DT)	Unlocked desktop MPUs
Broadwell EP (BDW-EP)	Xeon E5, Dual-Processor platform
Broadwell EX (BDW-EX)	Xeon E5, Multi-Processor platform, QPI
Broadwell E (BDW-E)	High-End Desktops (HEDT)

Architecture

Broadwell is for the most part identical to Haswell with server enhancements.

Key changes from Haswell

• ~5% IPC improvement
• FP multiplication instructions has reduced latency (3 cycles, down from 5)
  • Affects AVX, SSE, and FP instructions
• CLMUL instructions are now a single μop, improving latency and throughput
• The second-level TLB (STLB)
  • Table was enlarged (1,536 entries, up from 1024)
  • 1GB page mode (16 entries, 4-ways set associative)
• Larger out-of-order scheduler
• Faster store-to-load forwarding
• Address prediction for branches and returns was improved
• Improved cryptography acceleration instructions

Core features maintained a 2:1 ratio of performance:power.

Graphics

• 50% higher sampler throughput
• Improvements for increased geometry, Z, Pixel Fill
• Direct X 11.2, OpenGL 4.3
• OpenCL 1.2 and 2.0 (with Shared Virtual Memory)
• Up to 24 EUs (20% addition, up from 20 in Haswell), 48 EUs on Iris Pro Graphics

Block Diagram

Memory Hierarchy

• Cache
  • Hardware prefetchers
  • L1 Cache:
    • 32 KB 8-way set associative instruction, 64 B line size
    • 32 KB 8-way set associative data, 64 B line size
    • Write-back policy
    • Per core
  • L2 Cache:
    • 256 KB 8-way set associative, 64 B line size
    • Write-back policy
    • Per core
  • L3 Cache:
    • 1.5 MB
  • L4 Cache:
    • 128 MB
    • eDRAM
    • shared with GPU (Crystal Well)
    • Iris Pro models only