Hardware interconnects for CPU/GPU/accelerator communication


1. NVLink

  • Developer: NVIDIA
  • Purpose: High-speed GPU-to-GPU and GPU-to-CPU communication.
  • Status: Active (used in NVIDIA Hopper/Ada GPUs).
  • Key Features:
    • Higher bandwidth than PCIe (up to 900 GB/s in NVLink 4.0).
    • Critical for AI/HPC workloads (e.g., NVIDIA DGX systems).
    • Supports multi-GPU shared memory and scalability.

2. UALink

  • Developer: Consortium (AMD, Intel, Google, Meta, Microsoft, etc.).
  • Purpose: Open standard for accelerator/GPU communication.
  • Status: Emerging (expected launch in 2024).
  • Key Features:
    • Aims to compete with NVLink as a vendor-neutral alternative.
    • Targets AI/data center workloads.
    • Designed for scalability and interoperability.

3. Intel QuickPath Interconnect (QPI)

  • Developer: Intel
  • Purpose: CPU-to-CPU and CPU-to-memory communication (pre-2017).
  • Status: Deprecated (replaced by Ultra Path Interconnect (UPI).
  • Key Features:
    • Used in Intel Xeon Nehalem/Ivy Bridge architectures.
    • Supported coherent multi-processor systems.

4. HyperTransport (HT)

  • Developer: AMD
  • Purpose: CPU-to-CPU and CPU-to-I/O communication (pre-Ryzen era).
  • Status: Deprecated (replaced by Infinity Fabric in Zen CPUs).
  • Key Features:
    • Used in AMD Opteron/Athlon processors.
    • Reduced latency for chipset communication.

5. Intel Xe Link

  • Developer: Intel
  • Purpose: Multi-GPU/accelerator communication for data centers.
  • Status: Active (Intel Ponte Vecchio GPUs, Falcon Shores).
  • Key Features:
    • Part of Intel’s Xe GPU architecture.
    • Competes with NVLink in HPC/AI workloads.
    • Supports high-density GPU clusters.

6. Scalable Link Interface (SLI)

  • Developer: NVIDIA
  • Purpose: Multi-GPU rendering for gaming/workstations.
  • Status: Deprecated (phased out post-2019).
  • Key Features:
    • Used bridge connectors for consumer GPUs (e.g., GeForce).
    • Focused on splitting rendering tasks, not scalable compute.

Key Notes

  • Active Technologies: NVLink, UALink (emerging), Intel Xe Link.
  • Deprecated/Replaced: QPI, HyperTransport, SLI.
  • Use Cases: NVLink/Xe Link for AI/HPC; UALink for open-standards acceleration; SLI/QPI/HT for legacy systems.

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