Setting up the High-Speed Multiplier

ENIAC's High-Speed Multiplier works by coordinating the action of from 4 to 6 of the accumulators.
In order for the Multiplier to work correctly it must be proplerly connected to these accumulators.

Here are the accumulators that the Multiplier needs to be connected to:

Accumulator Function
9
Multiplier
10
Multiplicand
11
Left Hand Partial Product I
12
Left Hand Partial Product II (Used for 20 digit answers)
13
Right Hand Partial Product I
14
Right Hand Partial Product II (Used for 20 digit answers)

In this tutorial you will learn all the connections that need to be made for setting up the
Multiplier unit.

We will start by setting up the Multiplier recieve pulses

Start off by selecting the Multiplier tab
Be sure that Panel 1 is selected
Turn the power On to this panel

Set the R alpha through R epsilon outputs to P5-A:1 through P5-A:5

Now we need to connect these pulses to the multiplier accumulator (9).

select the Acc tab
Select accumulator 9
Turn the power On to this panel

Set I1 through I4 to P5-A:1 through P5-A:4

Set the input of program 5 to P5-A:5

Set the program modes for programs 1 through 4 to alpha through delta

Set the mode of program 5 to epsilon

Next we need to connect the Multiplicand receiver pulses

Switch back to the Multiplier tab

Set the D alpha through D epsilon outputs to P5-A:6 through P5-A:10

select the Acc tab
Select accumulator 10
Turn the power On to this panel

Set I1 through I4 to P5-A:6 through P5-A:9

Set the input of program 5 to P5-A:10

Set the program modes for programs 1 through 4 to alpha through delta

Set the mode of program 5 to epsilon

Next we need to setup the product disposal pulses:

Switch back to the Multiplier tab
Select Panel 3

Set the A through ASC outputs to P5-B:4 through P5-B:9

Now we need to set the final product accumulator (13) to receive these pulses

select the Acc tab
Select accumulator 13
Turn the power On to this panel

Set the inputs to programs 5 through 10 to P5-B:4 through P5-B:9

And configure programs 5 through 10 as shown below

Next we to connect the pulses that are used during sign correction

select the Multiplier tab
Set the RS program output to P5-B:1
select the Acc tab
This connects to the multiplier accumulator, so select accumulator 9
Connect the input for program 6 to P5-B:1
Configure program 6 to mode S and set the Clear/Correct switch to 0
LHPP I receives this value, so select accumulator 11
Turn On the power to this accumulator
Set the input of program 1 to P5-B:1
Configure program 1 to mode beta and set the Clear/Correct switch to 0
Switch back to the Multiplier tab
Set the DS program output to P5-B:2
select the Acc tab
This connects to the multiplicand accumulator, so select accumulator 10
Connect the input for program 6 to P5-B:2
Configure program 6 to mode S and set the Clear/Correct switch to 0
RHPP I receives this value, so select accumulator 13
Set the input of program 1 to P5-B:2
Configure program 1 to mode beta and set the Clear/Correct switch to 0

The last program pulse we need to setup is the pulse used to combine the left and right partial
products into the final product

select the Multiplier tab
Set the F program output to P5-B:3
select the Acc tab
LHPP will be sending its value, so select accumulator 11
Set the program input for program 2 to P5-B:3
Configure program 2 to use mode A and set the Clear/Correct switch to C
RHPP will be receiving this value, so select accumulator 13
Set the program input for program 2 to P5-B:3
Configure program 2 to use mode gamma and set the Clear/Correct switch to 0

This takes care of all the program pulse connections. Now we need to connect all the digit paths

select the Multiplier tab
Set the LHPP I digit output to D5-A
Set the RHPP I digit output to D5-C
Now we will work on the accumulators, select the Acc tab
Start by selecting accumulator 9
Set the S digit output port to D5-A
Next will be accumulator 10
Set the S digit output port to D5-B
Next will be accumulator 11
Set the alpha digit input port to D5-A
Set the beta digit input port to D5-A
Set the A digit output port to D5-A
And finally accumulator 13
Set the alpha digit input port to D5-C
Set the beta digit input port to D5-B
Set the gamma digit input port to D5-A

At this point the High-Speed Multiplier is setup to produce 10 digit products. In order to produce
20 digit products, some additional steps are required

select the Multiplier tab
Set the LHPP II digit output to D5-B
Set the RHPP II digit output to D5-D
Now we will work on the accumulators, select the Acc tab
Start by selecting accumulator 11
Set the right accumulator association to 12
Select accumulator 12
Turn the power On to this accumulator
Set the alpha digit input port to D5-B
Set the A digit output port to D5-B
Select accumulator 13
Set the right accumulator association to 14
Select accumulator 14
Turn the power On to this accumulator
Set the alpha digit input port to D5-D
Set the gamma digit input port to D5-B

Now the High-Speed Multiplier is fully configured for producing up to 20 digit products.

Considering how much work it is to setup the Multiplier, it is probably a good idea to save your
setup so that you can use it as a starting point for setups that will use the Multiplier.

In the next tutorial we will look at how to acutally use the Multiplier to multiply numbers.