Quiz submission record for quiz6-2-2 at Thu Jul 29 10:47:58 2004:

Your Answer for Question 1:
EPC is a 32-bit register used to hold the address of the offending instruction which could include an overflow or an undefined instruction.
The cause register is used to store the cause of the exception.  It encodes bits to mean certain things so that for example the lower order bit signifies eihter an undefined instruciton or an overflow.
The two instructions that cause exceptions are undefined instructions which are detected when the next state is not defined by the op value of the instruction.  Arithmetic overflow also causes exceptions.	
	

Your Answer for Question 2:
Imprecise exceptions is when the computer does not associate a specific instruction with a correct exception.  A machine put the next instruction in the EPC after the exception and just let the operating system deal with the specific exception.	

Your Answer for Question 3:
The drawback of polling  is that it can waste a lot of processor time because processors are a lot faster than I/O devices.  The processor will read the status of the I/O device many times because it is so much slower.  Many times I/O devices are doing nothing and the processor will have to devote resources to check that the I/O device is doing nothing.

Your Answer for Question 4:
loop:	la $t0, 0xffff0000
	lw $t1, 0($t0)
	beqz $t1, loop	# restart the loop if not ready
	la $t2, 0xffff0004
	lbu $t2, 0($t2)
	move $v0, $t1
	sw $0, 0($t0)	#resets the ready bit to 0


Your unique submission ID is quiz6-2-2-cs61c-ee-1091123278-230.