IBM 3090 Computer Specifications

by Erik Devaney

The 3090 is a mainframe computer that International Business Machines, better known as IBM, first introduced in 1985. As a mainframe, the IBM 3090 consists of a large, structural frame that has all of its computing elements, like chips and processors, hanging or mounted inside. Engineers use the mainframe for processing data in bulk, which is incredibly helpful when it comes to -- for example -- analyzing statistics or carrying out financial transactions.


An IBM 3090 can store data using two distinct types of storage or memory: central storage and expanded storage. Central storage, also known as main memory, holds data that mainframe applications can freely access or share. In contrast, expanded storage is additional memory space, which means applications cannot access the data inside of expanded storage unless they first transfer the data to central storage. According to, IBM 3090 mainframes normally transfer data from expanded storage in 4K pages, pages of data that each have 4,000 pixels. The precise amount of storage in megabytes, or MB, that an IBM 3090 provides varies from model to model. The 300E model, as an example, has 128 MB of central storage and 128 MB of expanded storage. An IBM 3090's hard disk unit provides additional storage space. A disk unit can contain four, eight or twelve disks depending on the specific mainframe model, with each disk supplying between 3.7 and 22.7 gigabytes of storage.


The IBM 3090 has duplex functionality. This means its processors can duplicate and save data on two different hard disks, which decreases risk for losing data. However, unlike the more simplistic disk mirroring process, which relies on a single small computer system interface -- or SCSI -- controller for saving data on both disks, duplexing utilizes two independent or redundant SCSI controllers. This means if one controller is damaged, the 3090 can still access the duplicated data.


A "buffer" refers to a temporary location that computer mainframes use when transmitting data from one device or component to another. This helps sync components that operate at different speeds. The higher a mainframe's buffer speed, the more rapidly the mainframe can transmit data. According to The University of Tennessee at Knoxville, the IBM 3090 has a high-speed, 64 kilobit, or kb, buffer.

Operating System

The IBM 3090 functions using IBM's Multiple Virtual Storage/Extended System Architecture or MVS/ESA operating system. This operating system, however, acts as a guest on a virtual machine or VM operating system, which in turn relies on a Conversational Monitor System or CMS. CMS is an interactive system that allows users to run programs, edit files and complete other tasks that rely on user inputs.

About the Author

Erik Devaney is a writing professional specializing in health and science topics. His work has been featured on various websites. Devaney attended McGill University, where he earned a Bachelor of Arts in humanistic studies.

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