Hard Disk Monitor

HARD DISK MONITOR M. Noteris Prices of hard disks have fallen considerably over the past few years, and many useful CAD and DTP programs can not be run unless a hard disk with a storage capacity of at least 20 MB is fitted in the PC. Unfortunately, many PC users fail to realize that the huge amount of data on a hard disk is always in danger of being destroyed, overwritten or otherwise damaged by hardware faults or programs that behave erratically. The monitor circuit described provides a visual indication of a number of important control signals for the hard disk, and so helps to find out how this is used (or misused) by certain programs. PC users have good reason to start wor- rying when the hard disk falls silent after a series of rapid access operations by a program or installation procedure from the keyboard. In the worst case, the screen goes blank, and the machine no longer responds to keyboard commands. Die- hard PC users describe this condition as BRST (big red switch time...