I grateful to the many students at UW who used SPIM in their courses and happily found bugs in a professor's code. In particular, the students in CS536, Spring 1990, painfully found the last few bugs in an ``already-debugged'' simulator. I am grateful for their patience and persistence. Alan Yuen-wui Siow wrote the X-window interface.

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For a description of the real machines, see Gerry Kane and Joe Heinrich, MIPS RISC Architecture, Prentice Hall, 1992.

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These instructions are real-not pseudo-MIPS instructions. SPIM translates assembler pseudoinstructions to 1-3 MIPS instructions before storing the program in memory. Each source instruction appears as a comment on the first instruction to which it is translated.

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The MIPS compiler does not use a frame pointer, so this register is used as callee-saved register $s8.