Power ring
Beginner
A loop of thick power wires around a block or the whole chip, so electricity can come in from every side.
Novice
A loop of wide supply and ground wires around the edge of the chip’s logic area (the core) or around a large block such as a memory, so power can be fed in from every side.
Expert
A VDD/VSS pair on two upper layers, one layer for the horizontal sides and one for the vertical sides. Most useful when power enters from pads on the chip’s edge, and around memories and switched blocks. When bumps cover the whole chip face, they feed the top straps directly. Ring width is set by the current it must carry without wearing out.
Explained in Power planning (Design Flow).
See also: Power strap (stripe), Power delivery network (PDN).