Quiz submission record for quiz6-2-2 at Thu Jul 29 03:13:08 2004:

Your Answer for Question 1:
The EPC register holds the data of register that cause exception. The cause register tells us what type of exception the register has.
R-format instructions access EPC and Cause.


Your Answer for Question 2:
imprecise exception is the difficulty of always associating the correct exception with the correct instruction in pipelined computers.

Your Answer for Question 3:
it can waste a lot of processor time because processors are so much faster than I/O devices. THe processor my read the Status register many times, only to find that devices has not yet completed a comparatively slow I/O operation, or that the mouse has not budged since the last time it was polled.

Your Answer for Question 4:
memory-mapped I/O is a method that the processor is able to address the device and to supply one or more command e=words. This method can be used to transmit dara by writing or reading to select addresses.

loop:
li $t5, 2
li $t6, 3
la $t0, 0xffff0000
lw $t1, 0($t0)
beq $t1, $t5, loop
beq $t1, $t6, read
j exception  #the least two significand bits not equal                    
             #10 or 11

read: 
la $t0, 0xffff0004
lw $t1, 0($t0)
add $v0, $0, $t1


Your unique submission ID is quiz6-2-2-cs61c-aw-1091095988-421.