Technology - 308x, 309x, 9000 Series

Clockwise from upper left: 3081 (water-cooled, early 80's), 3090 (water-cooled, mid 80's), and 9121 (air-cooled, early 90's). Not shown: 9021 (water-cooled, early 90's), and Multi Chip Module (MCM from mid-range 4381 machine).

TCMs are big, as you can see. They are also quite heavy. They were built for very large mainframe computers. Each TCM contains many chips (up to 121 in the 912x) and an unbelievably complex multi layer cermic (MLC) substrate with interconnecting vias to enable all the chips to talk to each other. The many gold pins enabled 9 TCMs to plug into a "clark board" (a sort of sub-frame) and then some number of these large boards are put together into cabinet. (Anyone know where the name "clark board" came from? Is it in honor of a person named Clark?)

A "cooling hat" was bolted onto the water-cooled TCMs. Heat was transferred heat from the chips, into copper pistons, though the cooling hat, and finally into the water. The water was ciculated into cooling units and the cyle started over. On the air cooled TCMs, a huge heat sink bolted on. "Huge" may be an understatement, as the heat sinking apparatus for air-cooled TCMs looked more like HVAC equipment for a residence!

For a dissection of an air cooled TCM mechanism, try this link: Rob Storey's Retro Computing Pages.

Here is what the inside of a 9021 TCM looks like. Some chips are shown. The many-layer ceramic contains interconnections.

Below shows the back of a 308X TCM. This is where the water-filled cooling hat would have been bolted on.

Below is a group of TCMs in the Old Iron Gallery collection. 3081 on far right, 3090 on far left, various others in the middle, a few of which are shown without their aluminum housings.

Finally, below are a few TCM cooling "top halves." Inside are pistons (some copper, some aluminum). Each piston makes contact with a chip on the multi-layer ceramic substrate. The pistons transfer heat from the chip up into the aluminum heat sink and from their on to either circulating water or air for final removal. These TCM/piston assemblies were filled with a clear epoxy for display (to keep the spring loaded pistons from going s-p-r-o-i-n-g).