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.
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.
Training, consulting and other IBM mainframe services. Including hardware/software installation, systems programming and support services.
Mainframe application software development should be listed in Computers/Companies/Software_Development/Mainframes. Service companies also covering AS/400 or other platforms are listed at a higher level, such as Computers/Hardware/Systems/IBM. But service for PCs specifically when attached to mainframes would go here.
Companies that also manufacture IBM mainframe software or freeware are listed instead in Computers/Software/Operating_Systems/Mainframe/IBM/Software.