Mainframe Computers.

Mainframe computers were BIG
IBM Sales Photograph

This is an IBM sales photograph of a large mainframe computer. It has two Central Processing Units (CPU).
They are on the left, each is 6ft high (Sorry, 1.8 meters high).
They are both connected to the four RAM (Random Access Memory) core storage modules, (only three of which are in the photograph),
each containing 256 KByte of storage. The total RAM of this duplex configuration was 1 MByte.
(That may not seem much to you now, but then it meant 8 million ferro-magnetic toroids (doughnuts),
about the size of a "comma" on your keyboard. Each of which was threaded by three wires.)

Here is another photograph of a System 360 Model 67 computer as installed in Newcastle University in 1967.
It was difficult to get an overall view of the computer like in the IBM sales photograph,
the computer room was only so big, and even with a 'fish-eye lense' it would have been difficult to get it all in.
What you can see is:-
360/67 mainframe
On the right is the front of the CPU (Central Proccessing Unit) with its rows of blinking lights.
In those days you could stop the computer and single cycle it instruction by instruction.
By examining the lights you could see exactly what the CPU was doing.

The nearest computer operator is at the operator's console used
to issue commands to control the operation of the computer.
The one further away is changing a disk pack.
There was nine disk storage drawers, only eight of which could be active,
and each disk pack could store 30Mbytes, so the whole could store 240Mbytes.
The whole direct access storage unit was:
Length 4.7m Depth 0.8m Height 1.5m
Weighed 1727Kg
used 12.2KVA of electricity
and cost 101,250 pounds sterling in 1967.

Newcastle University had just five mainframe computers before VLSI, distributed computing, and the Internet took over.
Following is a table of the last three. Each occupied about 200 square meters.
(What is the ground floor area of your home? Mine is 132 square meters, and I know that is big,
but not enough for a mainframe computer!)

Computer Number of Weight Electricity From - To
Components Kg KVA
IBM 360/67 21 12,000 71 1967 - 1980 360 details
IBM 370/168 36 24,000 90 1975 - 1984 370 details
Amdahl 5860 44 17,000 81 1985 - 1992 5860 details

The IBM Sales photograph on this page is reproduced by permission of IBM.
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