Thermal Simulation Discussion 7/5/2017 Yueming Li, Thermal Engineer, Facebook John Fernandes, Thermal Engineer, Facebook Jia Ning, Hardware Engineer, Facebook

A-Cases Update Updated models for A cases 170705 Updated Mezz 3.0 Case A1 WO HS.pdml (cold-aisle) 170705 Updated Mezz 3.0 Case A6 WO HS.pdml (hot-aisle) Corrected QSFP model to minimize heat conduction from cage to PCB; corrected Mezz PCB sizes Comparison between with and without QSFP heat sinks for both normal operation and stand-by cases

Improving QSFP Cooling – MLX HS Cold Aisle – Normal Operation Cold Aisle – Stand-by Condition Adding HS can reduce the temperature of I/O modules by ~4-6 °C for cold-aisle cases. ASIC temperature will increase by ~3-7°C due to higher impedance.

Improving QSFP Cooling – MLX HS Hot Aisle – Normal Operation Hot Aisle – Stand-by Condition Adding HS can reduce the temperature of I/O modules for hot-aisle cases but not enough to pass.

Impact of Contact Resistance A few cases were studied Contact resistance can account for up to 5°C of the thermal budget

Discussion Topics Wind tunnel specification for vendors to share test data with adopters Feedback from the last meeting Definition of monitor points are important Wind tunnel setup should provide consistent results Request to community Share ideas/thoughts on wind tunnel specification Integrate shared PDMLs in system thermal models to better understand impact of current design(s)