In a nutshell: Microsoft has partnered with computer scientists at Carnegie Mellon University and the University of Washington on an initiative designed to limit the environmental impact of hardware used in servers. Dubbed GreenSKUs, the program uses memory and storage drives from decommissioned servers along with software tricks to give them a second lease on life.

Ashkitha Sriraman, a computer science professor at Carnegie Mellon that is involved in the program, notes that it is not uncommon for an entire server to be scrapped when just a single component goes bad or is not efficient.

The GreenSKU program seeks to identify RAM and SSDs that are salvageable, and reuse them in refurbished servers. Compute Express Link (CXL) controllers allow for the use of DDR4 or DDR5, and were crucial in helping to retrofit servers.

The team leveraged a pooling technique called Pond’s approach to cope with older memory featuring higher latency and less bandwidth, and used RAID striping to deal with slower solid-state drives. Specialized software was also deployed to identify tasks that are best suited to run on GreenSKUs.

On average, Microsoft replaces Azure servers every three to five years, regardless of whether or not they are still fully functional.

The reconditioned machines utilize AMD Bergamo processors, which were selected for their energy efficiency. Unfortunately, there’s no workaround to account for their lack of cache performance compared to the latest chips used in Azure servers. Of course, not every application requires cutting-edge performance.

“A lot of these applications do perfectly fine” on the refurbished machines, Sriraman said.

According to the Association for Computing Machinery’s Technology Policy Council, at current rates, information and communication technology (ICT) sector carbon emissions could exceed a third of all global emissions by 2050. At scale, the team believes their reuse technique could result in a 0.1 to 0.2 percent reduction in global carbon emissions. That may not sound like much percentage wise but as Sriraman notes, it’s a huge number and is comparable to all of the emissions from total smartphone use in the US.