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Mainframe

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Introduction

We all know a PC, probably heard of supercomputers. But mainframes are not so known.

When you watch television and see a movie with a big machine, or hear people talking to each other (at college) about a mainframe do you sometimes wonder what that is? What they are talking about? Then this page is intended for you.

This page is the first in a future series to explain what a mainframe is and how it evolved in history. Who were the pioneers and what companies were, and still are, involved.

How did and how do they look like? On this page are a few pictures of the earliest mainframes.

Mark I mainframe (1950's)

When you think of a mainframe do you think of a large computer? Right!

But how large is it and what does it do, and what is its place in the family of computers we know

	Quantum computers
	Grid computers
	Supercomputers
	Mainframes
	Mini computers
	Microcomputers
	Terminals
	Embedded computers

The ranking of a mainframe is as you can see almost at the top.

And because of the sheer development costs, mainframes are typically manufactured by a large company such as IBM, Amdahl, Hitachi.

Their main purpose is to run commercial applications of Fortune 1000 businesses and other large-scale computing purposes.
Think here of banking and insurance businesses where enormous amounts of data are processed, typically (at least) millions of records, each day.

BINAC(1960's)

But what classifies a computer as a mainframe?

• A mainframe has 1 to 16 CPU's (modern machines more)
• Memory ranges from 128 Mb over 8 Gigabyte on line RAM
• Its processing power ranges from 80 over 550 Mips
• It has often different cabinets for
  • Storage
  • I/O
  • RAM
• Separate processes (program) for
  • task management
  • program management
  • job management
  • serialization
  • catalogs
  • inter address space
  • communication

Historically, a mainframe is associated with centralized computing opposite from distributed computing. Meaning all computing takes (physically) place on the mainframe itself: the processor section.

(3)
IBM 4381 mainframe processor from 1985

Chronology

Building mainframes started with the MarkI soon to be followed by tens of other types and manufacturers. But as said earlier, because of the development costs only governments and large firms could pay for the development of such behemoths.

Have a look at some early mainframes:

1939

Atanasoff-Berry Computer created at Iowa State

1940

Konrad Zuse -Z2 uses telephone relays instead of mechanical logical circuits

1942

1943

Colossus - British vacuum tube computer

1944

Manchester Mark1

1946

J. Presper Eckert & John Mauchly, ACM, AEEI, ENIAC

1947

Harvard Mark II (Magnetic Drum Storage)

1948

whirlwind

Whirlwind at MIT

Manchester Mark I (1st stored-program digital computer),

1950

Univac I

Univac I first deliverey to the US Census Bureau

1952

Illiac I, Univac I at Livermore predicts 1952 election, MANIAC built at Los Alamos, AVIDAC built at Argonne

1953

Edvac

IBM 701

1954

IBM 650 (first mass-produced computer),

FORTRAN developed by John Backus

ORACLE-Oak Ridge Automated Computer And Logical Engine

Texas Instruments introduces the silicon transistor,

Univac II introduced

1956

IBM 704

1956

MANIAC 2, DEUCE (fixed head drum memory), clone of IAS

1958

Nippon Telegraph & Telephone Musasino-1: 1st parametron computer, Jack Kilby-First integrated circuit prototype; Robert Noyce works separately on IC's, NEC 1101 & 1102

1960

Paul Baran at Rand develops packet-switching, NEAC 2201,

Whirlwind-air traffic control,

Livermore Advanced Research Computer (LARC),

Control Data Corporation CDC 1604,

First major international computer conference

Stretch

1961

IBM Stretch-Multiprogramming

IBM709

IBM 7090 console

1962

First use of virtual memory in a mainframe computer.⁽⁴⁾

Control Data Corporation opens lab in Chippewa Falls headed by Seymour Cray,

Telestar launched,

Atlas-virtual memory and pipelined operations,

Timesharing-IBM 709 and 7090

1964

IBM 360

IBM 360-third generation computer family.

1965

The Sage System,

From the late 1990's mainframe manufacturers started to leave the mainframe market, thinking mainframe business to be less profitable. And then there was virtually only one of major importance left: IBM. And as the single (most important) manufacturer IBM could dictate its own prices and sales went up as well as profits. Not surprisingly IBM's innovations in new mainframe architecture left the rest far behind.
In due time this was observed by other computer manufacturers and since 2001 competition got stronger again.

Construction

In the early days output came via a paper tape.

Later by an array of burning lamps and when the vacuumtube technology became sophisticated enough to build a CRT output came by means of spots on the screen (see williams tube).

Operating systems

At first there was no operating system. Most machines were hard wired. Programming it meant rewiring panels and setting hundreds of switches to have the machine calculate a table.
The next years when programming languages became available and memory was no longer a problem programmers created operating systems. You no longer had to be an electrical engineer to program a machine like that.

That made it possible for scientists and other users to quickly make a program and get the results.

To take care of all this a mainframe needs a sophisticated Operating System.
And as you look at it closely also quite different from what you find on your desktops machine. Almost always text based terminals (no graphics) are connected to it. Also PC's can be connected to a mainframe with a special interface program - often called 3270 emulation.

But a mainframe does have some particular properties:

• It manages a large number of users
• Distributes the sheer workload that can be handled by the machine over different processors and in/output devices.
• All processes are running on the host and not on your terminal.
• Output is sent to your terminal through a program running (in background) on the host(mainframe). Nothing else goes over the line. It is like you are connected to a large computer by long wires. That is also the reason why it seems that your keyboard typing sometimes appears slower on your monitor then you actually type

Operating systems for mainframes are few in number: UNIX, Linux, VMS, Z/OS, Z/VM, VSE/ESA. The latter three are of IBM origin and all three: VMS, Linux and Unix also run on IBM mainframes(2)

However there are some dialects of VMS, Linux, and Unix running on different machines.

Programming mainframes

When the first programming languages like Cobol, Fortran and Algol were created every large company and institution could hire people to do the programming of administration or complicated scientific calculations. The atomic bomb project in Los Alamos was a prime example of doing calculations using computers, without it the project never had succeeded in time.

Pioneers

Many scientists have contributed to the mainframe computer as it is now. Things did not go as smooth and fast as it goes nowadays. Sometimes many items, mechanisms, or materials still had to be invented before things really got on their way. On line memory was a crucial phase in developing large computers. Also when timesharing was invented in the late 60's mainframe use exploded.

Companies

To create a mainframe one needed at least a few hundred thousand dollars to build the first types.
Later types of the 60' and 70's required a few million dollars and now depending on what capacities you need mainframes range between two three hundred to several tens of millions
It is reasonable to say that small companies can not afford to spent that kind of money to develop one machine or prototype.

Thus firms like:

Ahmdal (Hitachi)
Bull
Comparex (Hitachi)
DEC (Compaq)
Fujitsu
Hitatchi
IBM
ICL (Hitachi)
NEC
Siemens
Unisys
Sun

and the like were the only ones financially capable of developing mainframe machines.

As mainframe markets shrunk some companies were assimilated by their peers and other congregated into even larger firms.

Conclusion

A (modern) mainframe is still a very large machine, sometimes tens of square meters. Has usually more than one processor and loads of memory: often running between a few mega- to several hundreds Gb of RAM.
It has tons of disk space and other storage facilities in large size and quantities that are not normally found with mini or micro computers. And although it looks like hundreds of users are using the machine simultaneously it is all governed by a sophisticated time sharing system, hence: serialization. (per processor)

IBM 701 (1952)

Introduction | Chronology | Construction | Operatingsystems | Programming | Pioneers | Companies

Last Updated on July 12, 2004

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Footnotes & References