When a fault-on-fault condition arises in a data processing system which follows a backup fault procedure in the fault handling process, control is passed to dedicated firmware. Fault flags are reset and information vital to maintaining operating system control is sent to a reserved memory (which can be written to in limited circumstances) under firmware control. Control is then transferred to an Intercept process resident in the reserved memory which attempts to build a stable environment for the operating system to dump the system memory. If possible, a dump is taken, and a normal operating system restart is carried out. If not possible, a message with the vital fault information is issued, and a full manual restart must be taken. Even in the latter case, the fault information is available to help in determining the cause of the fault-on-fault.