Logisim CPU Project Erty Seidel Spring Term 2011.
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Transcript of Logisim CPU Project Erty Seidel Spring Term 2011.
![Page 1: Logisim CPU Project Erty Seidel Spring Term 2011.](https://reader036.fdocuments.in/reader036/viewer/2022082403/56649d755503460f94a5577a/html5/thumbnails/1.jpg)
Logisim CPU Project
Erty SeidelSpring Term 2011
![Page 2: Logisim CPU Project Erty Seidel Spring Term 2011.](https://reader036.fdocuments.in/reader036/viewer/2022082403/56649d755503460f94a5577a/html5/thumbnails/2.jpg)
Logisim
• Logic Simulation Program– http://ozark.hendrix.edu/~burch/logisim/– Cross-platform ( > Java 5)
• Recent Update• Plugins and mods• FOSS (GPL)• [Demonstration]
![Page 3: Logisim CPU Project Erty Seidel Spring Term 2011.](https://reader036.fdocuments.in/reader036/viewer/2022082403/56649d755503460f94a5577a/html5/thumbnails/3.jpg)
CPU Project
• About one month• 60-100 Hours• 5 Versions (1 rebuild)• Still in development• SVN repository• Probably should have been doing homework
![Page 4: Logisim CPU Project Erty Seidel Spring Term 2011.](https://reader036.fdocuments.in/reader036/viewer/2022082403/56649d755503460f94a5577a/html5/thumbnails/4.jpg)
Running a Program
• Consult MIPS instruction set• Write out binary code• Use windows calculator to convert to hex• Write to a text document• Load into I-mem and D-mem• Run!
![Page 5: Logisim CPU Project Erty Seidel Spring Term 2011.](https://reader036.fdocuments.in/reader036/viewer/2022082403/56649d755503460f94a5577a/html5/thumbnails/5.jpg)
What Works?
• [See Excel spreadsheet]
![Page 6: Logisim CPU Project Erty Seidel Spring Term 2011.](https://reader036.fdocuments.in/reader036/viewer/2022082403/56649d755503460f94a5577a/html5/thumbnails/6.jpg)
Big Problems?
• No support for I-format arithmetic• Registers cannot write and read at the same
time• Multiplication / Division are weird when
working with highest-order bit• No branching• No exceptions• No forwarding / hazard detection
![Page 7: Logisim CPU Project Erty Seidel Spring Term 2011.](https://reader036.fdocuments.in/reader036/viewer/2022082403/56649d755503460f94a5577a/html5/thumbnails/7.jpg)
The CPU
• [Demonstration]
![Page 8: Logisim CPU Project Erty Seidel Spring Term 2011.](https://reader036.fdocuments.in/reader036/viewer/2022082403/56649d755503460f94a5577a/html5/thumbnails/8.jpg)
Lessons Learned
• CPUs are serious business• Simple pipelining is easy, anything more is
very difficult• MIPS instructions are a bit arbitrary• The carry-in for signed subtraction must be 1
![Page 9: Logisim CPU Project Erty Seidel Spring Term 2011.](https://reader036.fdocuments.in/reader036/viewer/2022082403/56649d755503460f94a5577a/html5/thumbnails/9.jpg)
Thanks
• Prof. Evans– Helped talk through problems
• Jorge Seidel– Solved subtraction, mult/div issues