Underfloor


The computer room had a false floor, about 30" deep (762mm).
2ft square floor panels rested on columns making a space for cables to connect equipment.
The large black cables were electrical power. The large grey were computer channel cables.
The small white and grey cables were telecommunication cables, and the orange and copper cables
were fire alarm signal cables and wall socket power cables.

This mess of underfloor cables was a problem to control because when a new computer was installed
its cables overlaid the old computer cables. And then an even newer computer was installed
and its cables overlaid all others.
Before you knew it, you had a mess of three layers, or more, of cables -
some in use, some redundant.

One reason I was valued, well I wasn't actually because 'they' didn't know I did it,
was that I knew which cables could be removed, if need be by cutting them into lengths
that could be pulled out of the tangle underfloor.
Since I left in 2002 I don't know what is going on.


This is a photograph taken from 2/3rds down the computer room giving you some idea of its size.
On the right is a column of the tower, and on it is one of the 3 phase power supply cabinets.
To its left is a blue box containing a big 3 phase switch that could isolate power to it,
whilst within the cabinet were three rows of circuit breakers, one for each phase that controlled
the supply to the 25 single phase supplies under the false floor.
This was not a 'ring main' power supply, but a 'star shaped' power supply,
so that any power disturbance generated by one failing device would be reflected back to the panel
then distributed in diminished form to each of the supplies.

To the left of the column is a bank of six magnetic tape drives. To the left of them is a
computer operator, Janice Burke I think.
To the left are magnetic tape racks. Each magnetic tape was 2400ft long and written at a maximum
of 6250bpi so could store a maximum of 180MBytes, in fact they stored much less, maybe 20MBytes.


This a bit of mainframe computer being delivered. It was just one of tens of cabinets,
each needing to be craned in via a loading shaft to the Sub-Basement of Claremont Tower.
This particular delivery was the 'Rotary Convertor' for the IBM System 370/168 Computer in 1975.
It was not being loaded to the computer room, but the Rotary Convertor Room, which is where I
currently (2005), have my collection of computing artifacts.

Back to Amdahl Power