If high-end server market is ruled by the Xeon chips then the leader of lower-end microservers might be the historic Pentium processor with a revamped architecture.
As a matter of fact, the chip making giant Intel has recently started shipping the latest version of the Pentium chip which is based on Intel's Sandy Bridge architecture with 32nm-the dual core 350 with a clock speed of 1.2GHz along with 3MB cache.
As a typical feature of server chip, the 350 does not have any integrated graphics component, however, at the same time it has an "astoundingly low thermal design power" (TDP) of 15W. This is far below compared to any of the other chips by Intel except those on the Atom architecture.
At present it is the Xeon E3 chips which is dominating the market, despite this, Atom has been slated to be used in next-gen microservers, reported EE Times.
The Pentium family of Intel can be seen as synonymous with the chip making giant since 1993. These chips are considered as one level higher than the lowest-end Celeron series of Intel. In fact, in the past it has been also used in various servers in the form of Pentium III as well as Pentium II Xeon.