Raging Menace - MenuMeters
www.ragingmenace.com/software/menumeters
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
MenuMeters is a set of CPU, memory, disk, and network monitoring tools for MacOS X. Although there are numerous other programs which do the same thing, none had quite the feature set I was looking for. Most were windows that sat in a corner or on the desk