$$ * \,\,\,\,\,\,\,\,\,\,\,$$ Interrupt from $$CPU$$ temperature sensor (raises interrupt if $$CPU$$
$$\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ temperature is too high)
$$ * \,\,\,\,\,\,\,\,\,\,\,$$ Interrupt from Mouse (raises interrupt if the mouse is moved or a button is
$$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$pressed)
$$ * \,\,\,\,\,\,\,\,\,\,\,$$ Interrupt from Keyboard (raises interrupt when a key is pressed or released)
$$ * \,\,\,\,\,\,\,\,\,\,\,$$ Interrupt from Hard Disk (raises interrupt when a disk read is completed)
Which one of these will be handled at the $$HIGHEST$$ priority?
$$LOOP:$$ Load a byte from device Store in memory at address given by address register $$$\eqalign{ & Increment\,\,\,the\,\,\,address\,\,register \cr & Decrement\,\,\,the\,\,count \cr & If\,\,\,count!\,\,\, = 0\,\,\,go\,\,\,to\,\,\,LOOP \cr} $$$
Assume that each statement in this program is equivalent to a machine instruction which takes one clock cycle to execute if it is non- load/store instruction. The load-store instructions take two clock cycles to execute.
The designer of the system also has an alternate approach of using the $$DMA$$ controller to implement the same transfer. The $$DMA$$ controller requires $$20$$ clock cycles for initialization and other overheads. Each $$DMA$$ transfer cycle takes two clock cycles to transfer one byte of data from the device to the memory.
What is the approximate speed up when the $$DMA$$ controller based design is used in place of the interrupt driven program based input-output?
