text: The disk buffer is controlled by the microcontroller in the hard disk drive , and the page cache is controlled by the computer to which that disk is attached .
simplified: This interface almost always works at a different speed than that of the hard disk platter . In such a case , the disk buffer is used to store the data that comes from the disk , before it sent to the computer , or to store the data that comes from the computer before it can be written to the disk .