Abstract: A data processor 2 has privilege levels associated with it including a user level and a privileged level. The processor 2 also has multiple stack memories which can be used including one or more process stacks, a main stack and a deep stack. The stack memory to be used is de-coupled from the privilege level. An activation level state variable tracking the number of pending exceptions is held by the processor and used to modify which stack memory stores pending state values when an exception occurs. If the system is at a base level of activation, corresponding to currently no pending exceptions, then when an exception occurs the current state data is saved on the process stack with the main stack being available for the exception handling code. Particular exceptions can be flagged as requiring use of a deep stack rather than either the process stack or the main stack.

Abstract: An apparatus for measuring viscoelastic properties of rubbery materials is disclosed. The instrument comprises two opposed dies having temperature and pressure controling means, means for initiating oscillatory rotation of one of the dies whereby the sample is cooled during its residence between the dies and reheated whereby torque measurements are carried out during the period of cooling. A method for operating the claimed apparatus is also disclosed.