6.1 Basics

As mentioned above, Simics's configuration system is object-oriented. A Simics object is instantiated from a Simics class. The core of Simics defines some useful classes, but most of the classes (processors, device models, statistic gathering extensions) are provided by modules that are loaded by the simulator when requested.

For example, the x86-p4 module defines, not surprisingly, the x86-p4 class. Note that a module may define several classes. Since modules advertise the classes they define, Simics can load modules transparently as objects are instantiated.

A class defines attributes that represent both the static and dynamic state of the instantiated objects. The static state includes information that does not change during the simulation (like a version number in a register) while the dynamic state covers the part of the device that are affected by the simulation (registers, internal state, buffers, etc.).

Let us take the example of an x86-p4 processor and have a closer look at how it can be configured using attributes:

• We can create an object instantiated from the class x86-p4. Let us call it cpu0
• The attribute freq_mhz can be set to 1500. It defines the processor clock frequency (in MHz)
• The attribute physical_memory can be set to a memory space object, such as phys_mem0. This attribute points to the object that will answer to the memory accesses coming from the processor.

As you noticed, attributes may be of various types. A complete description is available in the next section.