I am following a project called the Commander X 16, a Commodore 64 inspired machine based on, but only somewhat compatible with it.
My question: Is such a retro inspired development in scope of this stack exchange group?
Expanding on wizzwizz4's answer and the comments on it:
Questions about the actual workings of the C64 are obviously on-topic, even if phrased as, "The Commander X 16 works this way; does the C64 work the same way?" (I would not necessarily suggest phrasing things that way, but it may be useful if you're referring to some good documentation on the X 16 that saves you a lot of explanation.)
When it comes to porting C64 code, "How do I do this on the X 16?" is not on-topic for the group. However, if your problem is that you have a chunk of C64 code and you don't understand entirely how it works, posting a "How exactly does this work on the C64?" question would be right on topic. You'd need to ask a separate question elsewhere if, once you understand how the code works on the C64, you don't understand how to achieve the same effect on the X 16.
So perhaps the general questions you should be asking yourself before posting here a question inovlving a "modern" system are, "Does answering this question require specific knowledge about a an actual retro system?" and, "Can I split this question into two, one for Retrocomputing dealing with the retro side and one for another more appropriate forum dealing with the new system side?"
EDIT: I've changed my mind.
After a month or two, and looking through the comment on this answer and the other answers, I find myself now agreeing with others who take a broader approach than I did above. Specifically:
I'm not going to change my original answer above so as not to invalidate the votes on it, but I no longer support my original answer above. this. If this were my question, I would accept tofro's answer.
¹And the 6502 itself passes in my personal opinion even though it's "modern, currently supported" hardware (the W65C02S from Western Design Center). By a reasonable interpretation of the on-topic page, even "how do I handle the 6502 ROR bug" would be off-topic here because that is a "question...about earlier versions of a current machine."
While not yet being a "real thing" atm, the X16 is purportedly supposed to have:
The design reminds me very much of an MSX computer, but with a MOS CPU.
These all require programming techniques no longer taught to developers - Where else should such questions be asked?
If it looks like a duck, walks like a duck,... I don't care what year it was built.
I'd say in general yes, BUT.
And that's a huge but. There must be close ties to what classic designs are/were. Mostly in Hardware, but as well for software. To me that would mean that this system has to be a classic one in the core - like in using a real (old fashioned) CPU. After that questions can be classified much like questions about enhancements to classic computers. After all, were is the difference between an Apple II getting a PCI bus interface to a Steckschwein doing the same? In both cases the task is to make the 65(C)02 somehow handling an external interface. As Tofro said "If it looks like a duck, walks like a duck, ..." (*1).
Using this as a base, we can apply the same rules on 'new-old' systems as on the genuine old ones - or emulators, which are, to some degree (more than I like) on-topic. And like with that we can define some clear forbidden zones like
And unlike mentioned in other places, I do not think that porting is an argument changing anything here. Either it's a question about the old system, than it'll already be on-topic. Or it's a question about (programming) the new, then it needs to adhere to whatever rules do fit within reason.
Some examples what I would consider or not:
This doesn't mean that there can't be questions that are valid for RC.SE, but they need to have a very tight focus that obviously (*2) applies as well to the original system.
Some may assume, that my position on this has turned, but that's not the case. If at all, it's a gradual shift due the way RC.SE evolves. My basic position is that RC.SE is about old systems - plus modern use of them. Think of it, this is named RETRO-computing, not CLASSIC-computing. I didn't like the term to start with, as it includes all the things made to look old while they aren't - like emulations. Systems like the X16 (which I think is a crappy design) do well fit the term retro in a positive manner, so I see them as includable - with caution.
*1 - Then it must be a swan - SCNR :))
*2 - That means in question already.