Arithmetic Components

The center of the computer is the Arithmetic and Logic Unit, but we also provide a simple adder component for use in computing branches and offsets. 

Module: Adder

    Simple unsigned adder of arbitrary size. No overflow checking 

Module: MIPSALU

    This is the most basic implementation of the ALU. It has only the most basic operations and no support for signed operations of overflow checking.

Module: MIPSALU_2

   This is a more complex ALU that supports the full complement of arithmetic and logical operations of both signed and unsigned varieties. In general, the only difference between signed and unsigned operations is the overflow checking. Signed operations perform overflow checking, while unsigned operations do not.  The lone exception is the Set on Less Than (SLT) operation.  Consider the following case:

SLTI SLTIU

$t0, $0, 0xFFFF $t1, $0, 0xFFFF

# $t0 = 0. SignExt(0xFFFF) = -1 (2's complement) # $t1 = 1. SignExt(0xFFFF) = 2^32-1 (unsigned)

This happens because the unsigned version compares the numbers as unsigned numbers, while the signed version treats them as 2's complements numbers.  It's worth noting that SLTIU still performs sign extension on its immediate.    

Note: Does not implement any shift operations.