modified 9 years ago

4 Input XOR Comparison

01:04:48

Both of these configurations are equal. But now to find out which one is faster, gotta go to Cadence :(

From Wikipedia:
"A chain of XORs—a XOR b XOR c XOR d (and so on)—is true whenever an odd number of the inputs are true and is false whenever an even number of inputs are true."

Edit:
After math, the delay for the bottom "tree" circuit is 20.65 RC.
The delay for the top "waterfall" circuit is about 28.29 RC.
Therefore, the number of gates that the signal passes through matters a great deal and gates delay.

published 9 years ago

mapplejacks

9 years ago

The second one is faster, i.e. it has the smaller maximum delay, assuming the gates are equal. This is because the longest signal path goes through 2 gates compared to 3 on the top.

Taz8du29

9 years ago

These aren't XOR gates ! Put 3 inputs high and look at the result !

Taz8du29

9 years ago

I've made a real 4 inputs XOR gate : http://everycircuit.com/circuit/6428102820364288

rocketeeter

9 years ago

@Taz8du29: Just learned from the wiki: "A chain of XORs—a XOR b XOR c XOR d (and so on)—is true whenever an odd number of the inputs are true and is false whenever an even number of inputs are true."

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