Please submit only hardware manufacturer sites, and sites that provide non-marketing-oriented information about IBM Mainframe computers. Subcategory "Services" is for sites selling consulting, training and other services. Sites on Software, with no Hardware component, belong in a subcategory of Computers/Software, typically in Computers/Software/Operating_Systems/Mainframe/IBM or a subcategory.
IBM Mainframe refers to any computer that is compatible with IBM eserver zSeries computers and their predecessors, dating back to the System/360 first announced by IBM on April 7, 1964. Compatible in the software sense: it will run the same operating system.