Quiz submission record for quiz6-2-2 at Wed Jul 28 21:36:24 2004:

Your Answer for Question 1:
The EPC register holds the address of the instruction that caused the exception.  

The cause register contains information about why there was an exception.  

EPC and cause are accessed by mfc0

Your Answer for Question 2:
Imprecise exceptions are exceptions that don't specifically say exactly what is wrong for the sake of simplicity.  It may return an address that is close to where the exception occured but not precisely at the address where the exception occured.

Your Answer for Question 3:
The CPU has to waste a lot of cycles even though the device might be inactive for a long time.  There is a lot of overhead cost for polling.  

Your Answer for Question 4:
Memory-mapped io is io that is controlled by registers at special memory locations.  

loop:
move $t0, $0
move $t1, $0
lui $t0, $t0, 0xffff
lui $t1, $t1, 0xffff
ori $t1, $t1, 0x0004
lw $t2, 0($t0)
move $t3, $0
slti $t3, $t2, 2
bne $t3, $0, loop
lbu $v0, 3($t1)




Your unique submission ID is quiz6-2-2-cs61c-ej-1091075784-521.