Pseudo-Channel Ping-Pong

Overview

The hbm_pc_pingpong kernel tests the internal routing logic of the GPU by forcing data to physically cross the Infinity Fabric crossbar switches.

Execution Mechanics

To stress the crossbar, data must move between completely different physical memory stacks.

• The kernel reads data from the first half of the allocated VRAM.
• It performs a bitwise inversion (~) on the registers to simulate a small workload.
• It then writes that data to an offset that is exactly half of the total allocation.
• This massive jump virtually guarantees the read and write operations land on different physical channels/stacks, forcing the data to travel across the internal fabric.

Target Subsystems

• Primary Target: Infinity Fabric / Crossbar network.
• Secondary Target: Unified Memory Controllers.

Failure Symptoms

Critical Failures

• Interconnect Throttling: The fabric overheats and downclocks, causing a severe drop in measured gigabytes-per-second.
• Fabric Instability: Data corruption across the internal SoC routing.