Nicola Belluti
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106 lines
3.6 KiB
Markdown
106 lines
3.6 KiB
Markdown
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title = "Introduction"
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weight = 100
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The *Little Computer* is a family of *Instruction Set Architecture* (ISA) based
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on the Von Neumann architecture, created by [Yale N.
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Patt](https://users.ece.utexas.edu/~patt/) and [Sanjay J.
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Patel](https://sjp.ece.illinois.edu/) to teach their students about computer
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architecture.
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The processors in this group are extremely simple and they all feature a
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*very* [RISC](https://en.wikipedia.org/wiki/RISC) instruction set; they all
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have a 16-bit address bus and a 16-bit data bus, except for the latest
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architecture of the series -- the LC-3b -- which has an 8-bit data bus.
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The most famous ISA of this family is without a doubt the LC-3, the third
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iteration of the architecture: on this specific ISA people made a
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[subreddit](https://reddit.com/r/lc3), a [Wikipedia
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page](https://en.wikipedia.org/wiki/Little_Computer_3), an [online
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emulator](https://wchargin.com/lc3web/) and it's the easiest to find online
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using a search engine.
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## Why am I doing this?
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The goal of this project is to make more people know about this family of ISAs,
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which I believe is ideal for learning about computer architecture, operating
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systems and programming languages.
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Obviously, the focus will be on the last two iteration of the series, the LC-3
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and LC-3b, as they are the most recent, the most comprehensive, and, in my
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opinion, the most interesting.
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## Roadmap
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{{% steps %}}
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### 👷🏻 Writing of the Documentation
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The first step is to create a comprehensive documentation with a lot of
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sources.
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There isn't much information available about these architectures, so it is
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essential to refer to the original books and save what can be found online
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using the [WayBack Machine](https://web.archive.org/).
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### ◻️ Creation of a Developement Suite
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Once the documentation is complete, we can use it to create simple command-line
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tools, such as an emulator and an assembler.
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### ◻️ Developement of a GUI Learning Environment
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After developing a basic developement suite, we can create a graphical learning
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environment that can replace the outdated software created by the original
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authors.
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It would be great to create an environment where users can both write assembly
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and execute it, rather than having two separate apps.
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### 💪🏻 Physical CPU with an FPGA
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Inspired by [Ben Eater's series on the 6502](https://eater.net/6502), we could
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take the program and load it into an EEPROM to be executed by a physical
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version of our CPUs, maybe on a breadboard!
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It would be interesting to create a small custom motherboard with some sort of
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I/O interface to enable our computer to communicate with the outside world.
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### 💪🏻 Development of an LLVM Backend
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Let's access more modern programming languages such as C and Rust!
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### 💪🏻 Creation of a small UNIX-like Operating System
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### 💪🏻 Software Porting
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DOOM, MS-BASIC, Tetris... the more, the better!
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{{% /steps %}}
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## Licenses
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This project is entirely open source!
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This documentation is distributed under the [Creative Commons
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Attribution-NonCommercial-ShareAlike
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4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/) license and the source
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code is distributed under the [GNU Affero General Public License
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v3.0](https://choosealicense.com/licenses/agpl-3.0/). Feel free to take my
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work, study it, modify it, improve it and redistribute it ;)
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If you feel generous, please open a PR on the project's GitHub page so that
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everyone can benefit from your contributions.
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<br>
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{{< hextra/feature-grid cols=2 >}}
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{{< hextra/feature-card
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title="Little Emulator"
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icon="github"
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subtitle="Check out the project's code!"
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link="https://github.com/little-emulator"
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>}}
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{{< /hextra/feature-grid >}}
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