Professor Simonson

How Computers Work

CSC 195

Quiz 3 - 10 points

This is due by Thursday, midnight April 26.   You should hand in your drawings directly to the TA, or submit a scanned or digital version to the dropbox.

1. (2 points) You are designing a machine language that has 50 commands (op codes), 6 address modes, and where each instruction is stored in 32 bits.  How many bits can be used for memory (parameter) references?  How far away can a memory value be from an instruction that references it? (Recall that the data might be located forward or backward from the current line)

2. (8 points) Draw a formula and a circuit to implement the full adder we discussed in class. Recall that this circuit has three inputs and two outputs.  How many gates are in your circuit?  If each gate takes 0.1 nanosecond (1 ten billionth of a second) for electricity to get through, how long does it take for a full-32-bit ripple-carry-adder to send out its answer and carry?  Calculate carefully. (Recall that a 32-bit ripple carry adder is built out of 32 full adders.)