In this model, all variables, by default, reside in the internal data memory of the 8051 system. (This is the same as if they were declared explicitly using the data memory type specifier.) In this memory model, variable access is very efficient. However, all objects, as well as the stack must fit into the internal RAM. Stack size is critical because the real stack size depends upon the nesting depth of the various functions. Typically, if L51 is configured to overlay variables in the internal data memory, the small model is the best model to use.