The complexity of modern processors together with the high
cost of their development requires that processor construction
be paralleled by the construction of a simulator to guide 
design decisions.  The major obstacle in using simulation to 
facilitate development of new architectures is that traditional 
simulation approaches are not flexible enough to permit easy 
extension or modification of the underlying simulation model.

In this paper, we exploit object technology to present the 
design and implementation of Sim286, an execution-driven 
simulator that emulates much of the functionality of the 80286 
processor.  Object technology facilitates construction of a
simulator for a processor by permitting each component of the 
processor to be represented directly in the simulator by an 
object.  The design and implementation of Sim286 is accomplished
through extension and modification of an existing simulator,
SIMx86. The design of SIMx86 makes effective use of object 
technology and we exploit the extensibility and ease of 
modification of this design to facilitate the construction of 
Sim286.