File No. S370"'00
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Twenty-Eighth Edition (April 1988)
This major revision obsoletes GA22-7002-26. Changes or additions to the text
and illustrations are indicated by a vertical line to the left of the change. This
edition adds or deletes information about IBM products listed in the Summary
Changes are made periodically to the information herein; before using this publica-
tion in connection with the operation of IBM equipment, refer to the latest IBM
Systeml370, 30xx, 4300, and 9370 Processors Bibliography, GC20-0001, for
the editions that are applicable and current.
References in this publication to IBM products, programs, or services do not imply
that IBM intends to make these available in all countries in which IBM operates.
Any reference to an IBM program product in|