Sonja’s Story about Cray-1 fabrication and assembly

After seeing these pictures that seem to have the wire-mat showing on the module side of the frame I asked Sonja about the Cray-1 construction process:

Sonja’s Story

A little history you might already know: Seymour Cray was working for Control Data. I believe he wanted to build ‘his’ computer but CDC was going in a different direction so he left CDC to start his own company, basically in his back yard. The people that will be at the 50th anniversary party here could tell you a LOT more.

I worked at Fabri-Tek before Cray, and we would string wire through memory cores. We did this for many different companies. I worked there until they left town (not sure what happened there). One of the ‘important’ guys at Fabri-Tek then started a company called Chip-Tronic. We would string memory cores at our homes and turn them back when we were finished. They would check them out and if there were mistakes, they took 50 cents from our pay – I don’t remember what we would get for a completed board but I can say I rarely lost any of the 50 cents back to them.

So, after Chip-Tronic did not have work, Seymour Cray was starting his business and he looked to Chip-Tronic for workers. The first 2 years I was at Cray (building serial 1) was done while I was still an employee for Chip-Tronic. Seymour decided that he would actually ‘start’ his company and they hired ALL of us on Nov 1, 1976. Seymour was ‘employee’ number 100 and I was employee number 196.


The aluminum chassis would be delivered to us as a 4 column assembled frame.

The Career Development Center is a facility that employs developmentally or otherwise disabled people. (still operating today ) The Center would be sent a mixture of silver, black and red wire harness bars. They would then attach a wire connector with 48 blue/white twisted wires on it, to each side of the bar using 4 screws size 080 on each side. Once the wires were attached to the bar they would then ‘wrap’ the wires alternately one at a time. When they were finished, they shipped the assembled wire bars to Cray and we would install them into the chassis. Starting at the bottom we would install location number 71. Next would be location 70 and that would be a red bar. We would continue up with all locations ending in 5 being black and all locations ending in zero being red. All others were just the silver bar. The 2 in the middle of the chassis are both red for 0-0 locations.

Once all 4 columns had wires in them, the chassis was then laid down and we could ‘see’ all of the connectors and the wires were wrapped and hanging on the underside. We would search for a certain wire EX: A24-32 going to A30-48. These wires were called out to be 8 inches long so we would cut each wire at 4 inches and strip the ends to the length shown on the electric wire stripper (the other tool you referred to with the heat gun). Then we would get a solder sleeve at put it on each of the 2 wires. We would then use the heat gun to melt the solder.  Four people could work on the chassis at the same time.

We would complete a certain number of ‘shorter’ wires and then the chassis would be stood up. Once it was stood up, we had a tool with a battery with 2 wires and a rod at the end of each wire. There was a socket at the end of the rod and we would put a small ‘pin’ in the socket. The pin had a small spring inside it so as you place the end on the wire pin it would not damage the pin. You would use the information from the wiring pages, and put one end of the tool on wire number A24-32 and the other on A30-48. If it was wired correctly the light would light-up. If it did not light, someone would check it on the other side and repair it. After all wires were ‘buzzed’ the chassis was stood up. We would continue wiring until it was getting difficult to ‘find’ the correct wires.

After the wiremat would get thick, we would stand the chassis up and finish the wiring that way. Then there would be 2 people on the wiremat side finding the required wires and these people would cut the wire to the length stated. They would then send the wire through to the person on the wiremat side  and she would strip them and solder them together.

When a 4 column chassis was all wired, the remaining wires would be cut to 3 inches, capped with heat shrink and pushed through to the wiremat side, leaving a clean column where the module will be installed.

Just a little information – the wire strippers were quite heavy and they seemed to ALWAYS find their way to the floor and once dropped, the ends were broken and needed to be replaced. We went through a LOT of stripper ends. WELL – I mostly worked 3rd shift at Cray for the first 5 years, and my husband and I had a car lot. We would go to the Twin Cities (Minneapolis/St Paul) for either parts or something. While I was at one of the mechanic garages, I saw that they had their tools on a retractable electric wire spool hung from the ceiling. I thought HMMM – why don’t we use that at Cray. So I came back with the suggestion and it was a big hit. We no longer dropped our strippers as they were hanging just above our heads and the heat guns were hung too. There are many photos where you can see all the tools hanging over the people working.

Sonja Gardener from Chippewa Falls


Cray-1 wire assembly room sometime known as the Jungle.
Cray-1 wire assembly
Wiring mat work in progress
Working the night shift
Later machine assembly ( red & white wires often seen on YMP class machines)
Module stack showing rear wiring and cooling tubes in the frame.
Module stack showing rear wiring and cooling tubes in the frame. The black and red markings are on the 5 and 10 count from the base.

Working the night shift.

Module stack section from front

2 thoughts on “Sonja’s Story about Cray-1 fabrication and assembly”

  1. Avatar photo

    Jim From Australia adds : I only ever saw them wiring up columns that were in the horizontal position, as the ones in the background are. I spoke to several of these ladies and remember being shown how they put in each wire. They had stands next to where they worked that held folders open to where they could easily see them. The folders held the information about where each wire went from and to as well as, most importantly, how long the wire must be. They inserted the first wire into the connector and then inserted another wire into the other connector. They then used a metal yardstick to measure out the length of wire that they needed to insert so that the run was the correct length. I remember thinking that it was odd that they were adding wire in because the signal timing delay was so critical, but the yardstick was marked in inches!

  2. Charles m Clark

    I read Sonya’s wire assembly description with great interest and the photo entitled “Cray 1 wire assembly” shows clearly
    why this room was affectionately known as “The Jungle”. With all the heat guns and wire strippers hanging down from the
    I suggest that this tidbit is added to the photo title because it is folksy and interesting. Feel free to check with Sonya to make
    sure I am not making this up.

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