We selected the Mint simulator to run our multiprocessor simulations, based on its well-developed facilities for modeling memory behavior and its reasonably good performance. Since our target processor is the HP PA RISC, rather than the MIPS processor that the original Mint simulates, we implemented a variant of Mint, which we call Paint, that simulates the HP architecture. In addition, we made significant performance improvements to the basic simulation engine (common to both Mint and Paint). Finally, we extended the basic simulator to support both multiple executable files (as opposed to the original Mint's single executable), to support multiple processes per simulated processor (as opposed to original Mint's single process per processor), and to support simulating operating system code and system calls. All of these extensions were necessary to provide realistic measurements necessary to support our design and evaluation efforts. In particular, the ability to simulate interrupts, preemptive multitasking, and context switches allows us to account for the overheads and memory interference such activities incur on real systems. We have just begun the process of modifying Paint to simulate the complex internal structure of the PA-8000.
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