Amdahl Circuitry

The AMDAHL 5860 had a 24 nanosecond machine cycle time
with a bus width of 72 bits - 64 data bits and 8 bits of parity.
Keep this bus width in mind when you compare the VLSI processor chips
that obsoleted the mainframe, they had a bus width of just 8 bits
but much, much faster, because of shorter interconnections.

The Amdahl mainframe with its covers open.
At the top left is a control panel, and below it
three power supplies.These took high voltage
alternating current and converted it to low voltage
direct current. They were heavy! See www?

To the right is a gate containing 40MByte of RAM.

To the right of that is the CPU (Central Processing Unit),
called The Stack and below it its power supplies.
The Stack was connected by the large red ribbon cables
to the RAM and I/O channels.

We have one of the power supplies described Here

We have The Stack in the collection

This is a close-up of The Stack.
Its side is a multilayered printed circuit board
around which are (blue) sockets
to which the ribbon cables connected.
In addition to the multilayers is a gossamer
top layer of back wiring.

To the right and at the bottom
can be seen three of the bus-bars
that delivered electricity to the Stack.

Here is a view of The Stack, side on left, front on right.
In the front can be seen 13 boards end on.
In earlier mainframe configurations these boards
would have been in a single plane of rows and columns
mounted in a gate that could be swung open for access.
But this meant that there were long connections between boards
and long connections meant slower speed.

In the AMDAHL 5860 the boards were one above the other
connected by two busses, 12 layer printed circuit boards
one on each side, meaning shorter connections,
meaning faster speed.

This is a view of the rear
it is not just a piece of electronics
but a piece of engineering.

In the end the Amdahl was unceremoniously
craned from the computer room, cabinet by cabinet,
into, big, battered, dirty wagons, with no care
and driven off in a haze deisel fumes.

We had treated the Amdahl almost with reverence
just to touch it was an privilege
to actually open it up and pull bits out
was unthinkable
except to the Amdahl engineers.

This is a direct front view of the Stack
with one of the eight boards withdrawn.

The boards were called MCCs (Multiple Chip Carriers)
are 14 layer printed circuit boards
that accomodated both LSI RAM and Logic chips to
implement an entire system function. The LSI RAM chips , (with an access time of 7.5 nanoseconds - 133 Mhz),
provide storage for registers, buffers, and control stores.
The Logic chips contain 400 circuits and have an average
switching time of 400 pico seconds.

The Stack could accommodate twelve boards
so four board places were replaced with Bakelite blocks,
because the whole Stack had chilled air
blown through it to take away the heat
and the designers did not want the chilled air
to go through the vacant spaces.
They wanted it to go through the spaces between the boards
where the 'black' cylinders are.

This is a close-up of one of the boards
and the black cylinders. They are heat sinks.
Each heat sink is glued to a white square chip.

The chips on the right with four narrow heat sinks
are LSI RAM chips. Those on the left with a single large
heat sink are Logic chips.

The chips use Emitter Coupled Technology,
which though fast, used a lot of electricity,
so generated a lot of heat that had to be dispersed.

This is a cloe-up of the ECL chip connections.
There are 21 on each side, so 84 in total.

This is a photograph of the side of the board
there are three blocks of connections on each side.
Bear in mind these are the sides of the boards
when it is inserted into the body of the Stack.
How are the connections made?

This is a close-up of one of the three blocks,
it has 32 x 6 gold plated pins, totalling 192 pins.
Three blocks this side and three the other means 1152 pins,
all have to be perfectly made if the CPU is to operate.

This is a rear view of the 14 layer printed circuit board,
but still needed a deal of back wiring.

Each board measured 11" x 13" and could accomodate
121 LSI chips (over 48,000 circuits).

This is the rear of the Stack.
At the bottom is the connectors
for the power cables.

There are nine bus-bars
each heafty bits if copper.

On the left side is a label ...

Here it is, enlarged and rotated.
It says:

MODEL	STACK ASSEMBLY
PART NO	52- 102414- )00( C		V
SER NO	365	#	Kg
DATE	1985-06	kVA	k??

There is interesting information here.
Unfortunately not the weight or power KVA consumption.