Simulated Processor Project similar to 6502

Discussion of development of software for any "obsolete" computer or video game system.
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Joined: Mon Dec 30, 2019 1:50 pm

Simulated Processor Project similar to 6502

Post by clbx » Mon Dec 30, 2019 1:57 pm

Hi NesDev

For the past few months my partner and I have been working on a project for school in which we developed a home-brew simulated processor that works similarly to the 6502 found in the NES. I've been posting the project as many places as I can in an effort to get feedback both on code-quality and the design the processor architecture itself. This forum being filled with tons of people knowledgeable about the subject of the project, would be a good place to post

The goal of the project was just to make our own processor architecture, now we're branching out in how to make things for the system that would allow its to work as a computer of the time or like the NES, writing software for it.

Any and all feedback is greatly appreciated!!

Link to project:

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Location: Southern California

Re: Simulated Processor Project similar to 6502

Post by Garth » Sun Jan 31, 2021 10:12 pm

I didn't see anything about how you plan to handle indexing, with or without indirection. Is there a plan for that? (absolute indexed, indirect indexed, indexed indirect)

The AnyCPU forum would be a good one to post this on.

Making assembly language easier or more readable appears to be one of the goals. See my article on nestable program flow control structure macros at . They raise the level of the language a lot with, in most cases, zero penalty in run speed or memory taken, because they assemble the same thing you would by hand anyway, except that you don't have to look at the internal details every time. They make the programmer more productive, the code more readable and maintainable, and reduce bugs because you can see what you're doing better and spot problems more easily. There's more explanation of how the macros are formed in section 17 of my 6502 treatise on stacks (plural, not just the page-1 hardware stack), titled "Forming nestable program structures," at, and longer examples of their use in the last 40% of my page on simple methods of multitasking on the 6502 without a multitasking OS (or where hard realtime requirements would rule one out anyway), at . I provide source code for the macro definitions there, for the Cross-32 assembler, which I would recommend anyway because for $99 you not only get a great macro assembler for dozens of processors, but they even give you the information to adapt it to a processor of your own design.

BTW, since this comes up many times in your github pages: It's (with the apostrophe) specifically is short for "it is," or, less often, "it has," as in "it's been ten years since..." If you mean relating or belonging to "it," there's no apostrophe. lots of 6502 resources

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