Quiz submission record for quiz6-2-2 at Thu Jul 29 07:56:47 2004:

Your Answer for Question 1:
The EPC register holds the address of the affected (offending) instruction.  The cause register records the cause of the exception.  They help process exceptions.  R-type MIPS instructions and instructions other than beq and j access EPC and Cause.

Your Answer for Question 2:
Imprecise exceptions are relazed requirements of associating the correct exception with the correct instruction in pipelined computers.  It's left up to the operating system to determine which instruction caused the problems.

Your Answer for Question 3:
Polling can waste a lot of processor time because processors are so much faster than I/O devices.  We also have to determine whether the operation by a device was successful after its completion.

Your Answer for Question 4:
Memory-mapped I/O is a a way to address and give commands to an I/O device.  Portions of the address space are assigned to I/O devices, and reads and writes to those addresses get interpreted as commands to the I/O device.


($t0 = interrupt enable, $t1 = currentindex , $t2 = current value) 
Loop:
   beq $t0, $t2, exit
   add $v0, $v0, $t2
   addi $t1, $t1, 1
   lw $t2, 0 ($t1)  
j Loop
exit:


Your unique submission ID is quiz6-2-2-cs61c-cl-1091113007-3265.