- Slides: 5
Transferring Data – Primary Memory to Secondary Storage AS Computing
• This exact question has come up in 2 previous past papers, and can be worth 6+ marks. • “Describe the use of interrupts and buffers when data is transferred from primary memory to a storage device. ”
Define Terms • • • Primary Memory – RAM, IAS Secondary Storage – USB Memory Stick Both transfer data at different speeds Therefore need to use Buffer – Area of temporary memory used to transfer data between 2 devices • Interrupt – Method of stopping the CPU so it can perform a task and return to the previous task.
Key Points • • • Data sent to buffer from primary memory. This allows processor can continue with other tasks Interrupt sent when buffer is full. Buffer is emptied to storage device. Buffer used to allow RAM and secondary storage device to transfer data as they do so at different speeds. When buffer is empty Interrupt is sent to processor To request buffer refill Process cycles until all data is transferred
Additional Points • Error checking takes place once data is transferred. • Interrupt given priority to CPU when buffer is full, required refilling • Plan your answer. Use clear English. Read it first before writing on question paper. EXAM Technique!