What is SSI CEB form factor?

"The Compact Electronics Bay Specification (CEB) is a standard form factor for dual processor motherboards defined by the Server System Infrastructure (SSI) forum. The specification is intended for value servers and workstations based on the Intel XEON processor.

An SSI CEB motherboard is 305mm x 267mm [12” x 10.5”].

The SSI CEB specification was derived from the EEB and ATX specifications. SSI CEB motherboards have the same IO connector area and many of the same motherboard mounting holes as ATX motherboards, although SSI CEB motherboards are larger in size than ATX motherboards and have different processor mounting holes. The rear panel aperture is identical to the EEB and ATX specification and expansion cards mounted on an SSI CEB motherboard appear much the same as they would on an ATX motherboard.

To standardize thermal behavior of such motherboards, the position of the processors is defined, including the identification of the primary processor and the secondary. For motherboards with only one processor, it is recommended that the primary processor should be provided first."

via wikipedia http://en.wikipedia.org/wiki/SSI_CEB