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Building Your Own Machine The Universal Machine (UM) Introduction

COMP 40: Machine Structure and Assembly Language Programming. Building Your Own Machine The Universal Machine (UM) Introduction. Noah Mendelsohn Tufts University Email: noah@cs.tufts.edu Web: http://www.cs.tufts.edu/~noah. COMP 40 R oadmap. Building Useful Applications in your Language.

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Building Your Own Machine The Universal Machine (UM) Introduction

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  1. COMP 40: Machine Structure and Assembly Language Programming Building Your Own MachineThe Universal Machine (UM)Introduction Noah Mendelsohn Tufts UniversityEmail: noah@cs.tufts.edu Web: http://www.cs.tufts.edu/~noah

  2. COMP 40 Roadmap Building Useful Applications in your Language Ramp up your Programming Skills Big programs that teach you abstraction, pointers, locality, machine representations of data Building a Language Processor on your Emulator Intel Assembler ProgrammingThe Bomb! Emulating your own hardware in software

  3. Introducing theUniversal Machine

  4. Why work with the UM? • AMD64 is complicated – UM has 14 instructions • Easy to implement (HW or SW) • Learn more about assemblers and linkers • Learn to write assembler code • You will write an emulator for this machine – emulation is a wonderful and important technique! • The term UM traces to the work of Alan Turing Detailed specification for the UM will come with your next assignment

  5. UM Highlights • 8 32 bit registers (no floating point) • 14 RISC-style (simple) instructions • Load/store architecture: all manipulation done in registers • Segmented memory • Executing code lives in segment 0 • Programs can create and map new zero-filled segments • Any segment can be cloned to be come the new code segment (0) • Simple byte-oriented I/O • Does not have explicit: • Jump/branch • Subtract • Shift

  6. 14 UM Instructions • Arithmetic and data • Add, multiply, diviicde (not subtract!) • Load value • Conditional move • Logical • Bitwise nand (~and) • Memory management • Map/unmap segment • Segmented load/store • Load program • I/O • Input (one byte), Output (one byte) • Misc • Halt

  7. 14 UM Instructions • Arithmetic and data • Add, multiply, diviicde (not subtract!) • Load value • Conditional move • Logical • Bitwise nand (~and) • Memory management • Map/unmap segment • Segmented load/store • Load program • I/O • Input (one byte), Output (one byte) • Misc • Halt Add:$r[A] := ($r[B] + $r[C]) mod 232 Documented in the form of assignmentstatements (register transfer langauge – RTL)

  8. 14 UM Instructions Instruction Format 32 16 0 • Arithmetic and data • Add, multiply, diviicde (not subtract!) • Load value • Conditional move • Logical • Bitwise nand (~and) • Memory management • Map/unmap segment • Segmented load/store • Load program • I/O • Input (one byte), Output (one byte) • Misc • Halt OP R1 RB RC Add:$r[A] := ($r[B] + $r[C]) mod 232

  9. 14 UM Instructions Instruction Format 32 16 0 • Arithmetic and data • Add, multiply, diviicde (not subtract!) • Load value • Conditional move • Logical • Bitwise nand (~and) • Memory management • Map/unmap segment • Segmented load/store • Load program • I/O • Input (one byte), Output (one byte) • Misc • Halt 3 R1 RB RC 4 bits to selectone of 14 operations Add:$r[A] := ($r[B] + $r[C]) mod 232

  10. 14 UM Instructions Instruction Format 32 16 0 • Arithmetic and data • Add, multiply, diviicde (not subtract!) • Load value • Conditional move • Logical • Bitwise nand (~and) • Memory management • Map/unmap segment • Segmented load/store • Load program • I/O • Input (one byte), Output (one byte) • Misc • Halt OP R1 RB RC 3 bits to selectone of 8 registers Add:$r[A] := ($r[B] + $r[C]) mod 232

  11. What’s different from AMD64? • Very few instructions – can we do real work? • Pointers to words not bytes • Segmented memory model • AMD/Intel has I/O, but we did not study it • No floating point

  12. Next time we will discuss in more detail • Memory models and the segmented memory of the UM • I/O • How programs start and execute • Building complex instructions from simple ones

  13. ComputabilityandTuring-Completeness

  14. Emulators

  15. Emulators • Hardware or software that implements another machine architecture • Great way to learn about machines: • The emulator you write will do in software the same thing machines do in hw • Terrific tool for • Testing code before hardware is ready • Performance analysis (e.g. our testcachesim) • Evaluating processor/memory design before committing to build chip • Moving systems to a new architecture (e.g. Apple move from PowerPC to Intel)

  16. Question? • How would you implement an emulator for the UM?

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