Quiz submission record for quiz6-2-2 at Thu Jul 29 00:46:44 2004:

Your Answer for Question 1:
EPC(Exception Program Counter) holds the address of the affected instruction.

Cause register holds the cause of the exception. It used in recording of the cause of exception. 

mfc0, lwc0, mtc0, swc0 access EPC and Cause register.

Your Answer for Question 2:
The exception which does not satisfies following conditions:

1. PC is stored in known register.
2. All instructions before the PC-pointing address are excuted completly.
3. no instructions after the PC-pointing address are excuted completly.
4. We know the excution status of the instruction pointed by PC.


Your Answer for Question 3:
It can waste a lot of processor time, because I/O devices are much slower than CPU.

Your Answer for Question 4:
Memory-mapped io is a method of addressing the device. In memory mapped io, some part of address space are allocated to the device. We can control(I think communication will be better!) the device by reading & writing to this allocated memory space.

li $t0, 0xffff0000
li $t2, 1;
loop:
lb $t1, 0($t0)
andi $t1, $t1, 1;
bne $t1,$t2, loop
beq $t2, $0, read
li $t2, 0;
j loop
read:
lb $v0, 4($t0)



Your unique submission ID is quiz6-2-2-cs61c-bd-1091087204-325.