Introduction
Today we're going to be looking into the 6502 8-bit processor, and how you can emulate it using C++ on your modern computer.
This was a fun, little project that I really wanted to dedicate some time to as it would enable me to write more complex and specific emulators in the future for other processors.
You can view my project's source code on GitHub: https://github.com/alexanderwalford-official/6502-Emulator
Interaction
My source code will eventually feature a fully integrated graphical user interface to illustrate just how the 6502 is operating in real-time. This may become an invaluable learning resource for people getting interested in processor design & architecture.
Users should also be able to enter their own code for the processor to perform any operation that the original design would have been able to do.
Things To Consider
To write an emulator, we need extensive documentation on the device we are trying to emulate. This documentation needs to be as close to perfect as possible and we need all of the details of the processor's instructions and how it behaves under certain conditions.
If you don't have all of these details, you will likely need to infer some very complex and likely incorrect (not realistic) operations. However, some online research could certainly bring you much closer to your desired results.
You'll need to implement all of the standard operations of a processor if you aren't using some kind of library that does this for you; this is likely the place I'd recommend you start. This is also an essential part of the learning process, so it's better if you write it yourself.
The Challenges
You need to have a developed understanding of the C or C++ programming languages, this will enable you to write code that will not be too difficult to understand but also ensuring the performance of the application, keeping it as close to the real design as possible.
There are obvious performance overheads when emulating anything, luckily for us this won't be a problem with an 8-bit processor but do note that the overheads are linear as you emulate more modern processor designs.
Knowledge of hex will also be quite important, you don't need to be able to remember several codes but it's useful to understand the meaning of the hex codes.
Problems You'll Encounter
There is no doubt that you'll likely find this difficult if you've never done this before, I personally had never even considered emulating anything before but finally felt confident enough to attempt this project.
Online you'll find plenty of video tutorials where they walk you through every step of emulating processors or other devices, that's how I learnt how to write my 6502 emulator.
Do not just copy the code or copy and paste it from GitHub, you should try to learn how every line of code works and extensively appreciate the complexity of the work you are doing.
Conclusion
To finalise what we've mentioned in this blog post, writing an emulator is not an easy task but it's never a bad idea to start with the basics and make your way upward.
It's a brilliant learning experience and can really test your ability and knowledge of processor architecture design and implementation. It also looks great on your GitHub profile as it illustrates a deep understanding of low-level systems programming.
If you're just starting off, this probably isn't for you but if you're someone that's looking for a challenge and a way to expand your skillset; I could recommend doing something similar if not the same.
Let me know what your thoughts are and any emulators you may have written in the past.
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