True Story No9

 

Things just weren't as cool in those days!

We'd been working day and night to complete software changes and to finish testing a large message switching system.

It was a long time ago now but I recall the hardware comprised four or five rows of seven foot racks, each rack housed in a stove enamelled grey cabinet with chrome fittings and there were about a dozen racks in each row.

All this lot represented a mere five computers, working in a group, sharing common memory. The idea was that if one or two (or more if you were lucky) computers failed, service would be largely unaffected.

It was a Government Establishment and of course there were lots and lots of Civil Servants around.

The system had been delivered and its hardware commissioned a few years earlier, but as with most complicated systems, software bugs had kept it from being accepted by the customer.

In the 60s, computers were a bit different to those around today.

For instance a 32K store occupied two seven foot, nineteen inch racks....Nowadays, 32Ks worth of memory would be little larger than a pinhead.

Besides being very big, the system got fairly hot too.

In fact we needed a proper cooling system. This consisted of a large heat-exchanger on the roof, a chiller cabinet with lots of pipes and pumps (occupying one of the seven foot racks) and a network of ducts feeding the top and bottom of every rack.

There was a substantial false floor about eighteen inches deep in which ran the cooling trunking and masses of cables.

There was also a false ceiling carrying more cooling trunking and loads more cables.

Power supplies had much the same sort of voltages as are supplied inside your modern PC but we were supplying hundreds of amps via large copper bus-bars feeding all the racks, and within the racks, feeding the various electronic units.

I think there were some four or five units across the width of a shelf and probably about a dozen shelves in each rack. Each unit carried about twenty or so printed circuit boards and each circuit board had a few dozen transistors, dozens of diodes and lots of resistors and capacitors. I don't remember any integrated circuits but there may have been some in one or two of the newer units. These would have been nothing more complicated than simple gates or "D type" latches.

The day finally arrived when we were ready to demonstrate our handiwork.

Tests were scheduled to last for a week.

Later on, most of us had to go away in case we saw something we shouldn't, such was the nature of the messages that were being "switched".

The security of the free world hinged on the weeks results!

Lots of Senior Civil Servants appeared and gathered round a young Welshman who was the Project Leader.

Our MD arrived with his Project Manger.

It was a very very important day.

For starters we hadn't been paid yet. If we passed the test we got paid. If we failed there would be a lot of bother and we wouldn't get paid.

Zero hour was ten o'clock.

It was now 9:45.

The Government Project Manager arrived and the chief civil servant, Cliff, in charge of the computer room shook his hand and invited him and his entourage to view THE SYSTEM.

Cliff pauses by the grey cabinet at the end of the first row.

Still talking, he half turns and grasps the chrome handle of the cabinet and turns it.

There was a whooshing sound from the door seal and they all gaze into the depths of the cabinet.

By pure chance he's chosen the chiller cabinet and what would you expect in a chiller cabinet?

There before them, sitting on the metal pipes, which were white with frost, was a row of half a dozen milk bottles, some half full, others unopened, several plastic lunch boxes and sundry other items such as half-eaten loaves of bread and a bag of cream buns.

Cliff turned to look at the centre of interest and stopped talking.

There was a sudden silence.

I suppose, being a SENIOR civil servant someone had always brought him his tea and he'd never, in the three years he'd been there, thought about the logistics of it all.

He must have been a bit embarrassed because for a full two minutes he just stood there, with his lords and masters grouped around him, unable to get a word out, his face getting redder and redder.

Suddenly the silence was broken by a crescendo of noise.

A klaxon was sounding in short bursts.

A bell was ringing continuously.

Then without further ado everything went deathly quiet.

All that one was aware of was a large blue light flashing on the main power supply panel.

For the first time in three years the power had gone off!

Everyone knew, except Cliff that is, that one should never open the chiller cabinet door for more than a few seconds.

Just long enough to retrieve or replace one's milk.

The door is sealed, open it for longer than about 30 seconds and the cooling sensors detect something is amiss.

Longer still and something is definitely not right.

Open it for two minutes and the system shuts down because the sensors believe the cooling system has failed.

Either a million transistors start to fry or you remove their power.

The latter was the preferred option and that's what had happened.

No big deal you might say... Just turn the power on again and Bob's your uncle, the computers are all up and running again.

Well in those days it wasn't that easy.

To get the required speed from the old devices they operated flat out. Their different voltages had to be applied in a very special way. Lose the negative bias rail and a transistor will melt its junction.

Although automatic power sequencing was the order of the day, it wasn't quite perfect.

There were also millions of wire wrap connections.

Some had reached the stage were they relied on current passing through them to work... Maybe not many but enough.

There were diodes in the same shape... Losing their bias opened their junctions.

Nobody ever turned off a 1960s computer system of this size without at least a weeks work debugging it when it came on again.

This one took a week.

It was mainly poor wire wraps and duff diodes with the odd transistor thrown in.

The security of the free world would have to wait another week. So would getting paid!

 

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