Communications of the ACM

practice

IN 2011, FACEBOOK announced the Open Compute Project to form a community around open source designs and specifications for datacenter hardware.

Facebook shared its hardware specs, which resulted in 38% less energy consumption and 24% cost savings compared with its existing datacenters. 6 What Facebook and other hyperscalers (Google, Microsoft, et al.) donate to the Open Compute Project are their solutions to the agonizing problems that come with running datacenters at scale.

Since then, the project has expanded to all aspects
of the open datacenter: baseboard management
controllers (BMCs), network interface controllers (NICs),
rack designs, power busbars, servers, storage,
firmware, and security. This column focuses on the
BMC. This is an introduction to a complicated topic;
some sections just touch the surface,
but the intention is to provide a full
picture of the world of the open source
BMC ecosystem, starting with a brief
overview of the BMC’s role in a system,
touching on security concerns around
the BMC, and then diving into some of
the projects that have developed in the
open source ecosystem.
If the CPU is the brain of the board,
the BMC is the brain stem. It moni-
tors and manages the physical state of
a computer or hardware device. This
state includes temperature, humid-
ity, power supply voltage, fan speeds,
remote access, and operating system
functions. The BMC has historically
been a SuperH or ARM-based system
on a chip (SoC) with common function-
ality including but not limited to:

˲RMII (reduced media-independent interface) and RGMII (reduced gigabit media-independent interface) for ethernet.

˲ A boot flash with an SPI (serial peripheral interface) NOR. (NOR and NAND are types of nonvolatile flash memory; the difference is in the type of logic gate used.)