a) Explain the concept of 'interrupt' in the context of the CPU and some external 1/0 device, clearly outlining the micro-operations that take place before the Interrupt Service Routine is actually invoked. b) A device is of medium speed and always need to exchange 16KBytes (1KByte = 1024 bytes) of data with the system which must be done within 1 millisecond. A cycle stealing DMA scheme can provide approximately one cycle every four clock cycles to be 'stolen'. Estimate the minimum clock speed required in multiples of 100 MHz.