Image credit: Dan DeLong for Microsoft
Microsoft reported today it has successfully tested a new cooling system that removed heat up to three times better than cold plates.
The system is called microfluidics, an approach that brings liquid coolant directly inside the silicon. Tiny channels are etched directly on the back of the silicon chip, creating grooves that allow cooling liquid to flow directly onto the chip and more efficiently remove heat, according to a blog by Catherine Bolgar on the Microsoft site. The team used AI to identify the heat signatures on a chip and direct the coolant with more precision.
Most GPUs are cooled with cold plates, which are separated from the heat source by several layers that limit the amount of heat they can remove, Bolgar stated.
“Microfluidics would allow for more power-dense designs that will enable more features that customers care about and give better performance in a smaller amount of space,” said Judy Priest, corporate vice president and CTO of Cloud Operations and Innovation at Microsoft. “But we needed to prove the technology and the design worked, and then the very next thing I wanted to do was test reliability.”
According to Microsoft, its lab-scale tests showed microfluidics performed up to three times better than cold plates, depending on workloads and configurations involved. They said the technique also reduced the maximum temperature rise of the silicon inside a GPU by 65 percent, though this will vary by the type of chip. The team expects the cooling technology would also improve power usage effectiveness, a key metric for measuring how energy efficient a data center is and reduce operational costs.
Judy Priest
Although microfluidics is not a new concept, getting it to work has been a challenge. It requires ensuring that the channels are deep enough to circulate adequate cooling liquid without clogging while not being so deep as to weaken the silicon such that it risks breaking. The team produced four design iterations in the past year alone.
“Systems thinking is crucial when developing a technology like microfluidics,” said Husam Alissa, director of systems technology in Cloud Operations and Innovation at Microsoft. “You need to understand systems interactions across silicon, coolant, server and the data center to make the most of it.”
Getting the grooves right is a challenge. The microchannel dimensions are similar in size to human hair. As part of the prototyping effort, Microsoft collaborated with Swiss startup Corintis to use AI to help optimize a bio-inspired design to cool chips’ hot spots more efficiently than straight up-and-down channels, which they also tested. The bio-design resembles the veins in a leaf or a butterfly wing – nature has proven adept at finding the most efficient routes to distribute what’s needed.
Microfluidics also required designing a leak-proof package for the chip, finding the best coolant formula, testing different etching methods and developing a step-by-step process for adding etching to manufacturing the chips.
As a next step, Microsoft continues to investigate how microfluidic cooling can be incorporated into future generations of its first-party chips. It will also continue to work with fabrication and silicon partners to bring microfluidics into production across its datacenters, the company said.
“Hardware is the foundation of our services,” said Jim Kleewein, technical fellow, Microsoft 365 Core Management. “We all have a vested interest in that foundation – how reliable it is, how cost effective, how fast, how consistent the behavior we can get from it, and how sustainable, to name just a few. Microfluidics improves each of those: cost, reliability, speed, consistency of behavior, sustainability.”
