(Not sure if I got everything, but tried)
The question "what is DMA and how does it work?" is currently on hold as off-topic, showing that at least five RCSE users believe that it is. Is it really off-topic?
If so, why?
It carries not one but two marks to make it of-topic (but SE UI lets only select one).
It's a generic term, not specific to retro computing. As such it is per se not for RC.SE. To make it on-topic, it would need specific ties to explicite classic technologies and/or implementations (aka machines).
The "how does it work" in conjunction with such a generic term makes it automatic way to broad to fit the format either.
(Chenmunka just added an important further part her: "Shows no research effort" - it tackles this from another, more generic angle. I was somehow searching for this term the whole time I wrote this post. Thank you)
In particular, what clauses (both pro and against) of our topics list apply here?
No need to look up any list, as it can be done by common sense.
- If a question does ask about something that is generic, and not retro specific, it needs to be qualified in its retro aspect.
This can as well be supported from an opposite (answer related) angle as
- If a concrete (i.e. close tied to whats asked) answer can be given that answers the question in whole while staying specific (!), then the question may not be too generic.
Mind you, the last proof is not an exclusive, but complementary to the first - also neither removes the basic requirement to judge reasonable.
For example asking "I've heard that the NES uses 'DMA', what is this?" would still be a less than desirable question, but tied enough to a specific RC item to make a valid one. It can be answered with a single line about DMA in general (bus sharing between different masters) and then explain what DMA in case of the NES means.
This brings up another important aspect when judging Questions:
Does it (and its answer) benefit future readers in an RC related sense?
IMHO this is the second most important rule for a question - right after the primary one of an answer solving the issue the OP puts up.
Generic questions that are not RC specific do neither a good for the OP nor RC.SE. This isn't the place to write a whole world encyclopedia. They are best answered by looking at common sources (like Wikipedia) - which is IIRC even requested to be done before writing a question, isn't it?
In the mentioned case, the answer would either be just a sentence, thus not really satisfying, merely pointing to wholesome sources, or a way over the edge treatise covering DMA from mainframes of the 1960s all the way to todays PCIe bus implementation. If one intends to spend that time, I seriously suggest doing so in the Wikipedia, as it would be of way more benefit to everyone. He could even start from an already large base and just add whats missing.
What are other questions which might appear to be off-topic for similar reasons, and what is different about them that they should they not also be closed? (Or should they also be closed?)
Judging question isn't a task for a simple checklist. If that would work, we might have already implemented a script to do so. As with any real world decision, it's all about each individual case. And that#s the beauty of the SE principle. Everyone can raise a flag to mark a question as off topic,
And since no answer is complete without some analogies,
try to replace DMA in this sentence
"I've heard the term 'DMA' being used a lot in reference to older consoles."
by one word of this list and think about:
Does any of these generic terms get RC related just by mentioning it has been used with some older console?
And now for something complete different:
(well, not so much, but here specific to Curt's answer)
For everything mentioned during the first section: All nice, but hasn't been asked. Any answer beyond a basic "DMA is multiple bus masters" is better gathered from Wikipedia then writing a lengthy answer that (looking at Curt's points) will still be one sided and incomplete - if not missing the point at all.
Just take two explicite points:
The mentioning of "the not-insignificant cost of supporting DMA", which is plain wrong, or at best only relevant to some very specific CPUs. CPUs not supporting DMA right out of the box are a minority and usually special cases, like the 6502.
While being 'familar' with some aspect might be an issue, it's pure guesswork to go that lane. Solving missing knowledge about a basic concept of computing, not especially tied to retrocomputing is not a task for RC.SE.
For the examples given:
Memory Check: No,that isn't a generic question (asking for "what is a memory check" would be), not even one for hardware, but for the historic timeline as seen by him. So while the answers are rather technical, they follow that lead. And while the question may seam somewhat simple, it does hit exactly what I consider RC: Not (only) bit positions in a sprite register, but the history in context.
Z80 address test: I fully agree that a new Z80 machine would be at least borderline here. I have argued that several times, but had to accept that most others here have a different opinion. Having said that, the exact question is not about any new computer or chip (next to all old chips are still available), but the bus protocol of a classic CPU. This has been conformed as on topic several times. And I see no reason to differ here. Further, this question is, unlike the DMA one, not a vague call, that can be answered by entering DMA into Google, but a clearly formulated one related to RC knowledge.
BASIC-OS: While asking about still in use OSes might be questionable (I think they are fine), mentioning answers as primary reasoning is somewhat contradicting. Especially as this isn't, as I understand Curt's point, not about all answers and the question to be answerable within RC.SE, but some answers straying apart. That's complete 'normal' to be found in many questions. The SE system even offers a way to handle this by downvoting (*1).
Real Flat: That question is truly a beast of it's own. I have to full heartly agree, it does fit SO (the original SE.SE was clearly wrong) as a general x86 coding question. What I do not see is that the publication date of a book has any significance for on- or off-topicness. There are many brand new books about programming classic systems. So many, that it feels as if they outnumber contemporary publications.
Last but not least for the Volume Argument. It's not specific to Curt's answer but has been brought up by others as well. I do not think that it is a valid argument at all.
thinking of it, it is a quite good one: If it needs to be made, it automatically proves that a question is not on-topic at all. It's an argument that is only be made if there is no other to support the validity of a question, thus proving that the question is not fit for RC.SE.
Part of this argument is often pointing out that SE has certain thresholds for leaving Beta, number of questions being one of them. Just like any generic number applied to vastly different sites, it does neither good. Not every site does have the potential to attract large numbers of visitors, contributors and question givers. While it may be a setback to our ego: Some retrocomputing may be mainstream by now, serious dealing seams to be less followed.
So we will stay forever in beta-hell (doesn't fell like hell to me) - or not, as stackexchenge has recgnized the issue and already promoted several sites out of beta, despite not fulfilling all criteria. There is a chance for us. To go that way, we should focus on the things we seam to do right. That's good answers to relevant questions. Lowering standards instead may backfire.
Oh, and on a side note to the prelude, you seam to be obsessed with the score scheme. It doesn't matter if one answer gets 5, 50 or 500 points for some questions. As said in many places, they are only indicators, not anything to race for or nitpick about. They are just (if not less than) the icing on a cake. They are earned on each question separate and anew, helping to sort answers for future readers.
With a gamification like this, the game part is never important. Focusing on points never does any good. It usually leads to waste of energy in an imagined race, time that could be way better used to care for answers. It is, and always should be, about helping the OP with the issue he raised.
As for myself, I only care for giving an answer that helps the OP. Wherever possible exactly as asked, as the question wording reflects what the OP wants to know. If I suspect a deeper cause
*1 - Voting is maybe something we need to tackle again. Just not sure how. Fact is that while voting on questions is about personal taste, voting on answers is (or should be) about factual content. It seams that some use it more to voice a dislike with the answer, maybe when the information given doesn't fit their picture, or what they expect as an answer.
Similar Meta. I noticed Curt's answer got a downvote. While downvoting makes some sense on the main site, where it can be used to mark wrong answers, it's complete contra productive on Meta. Meta is not about right or wrong, but about opinions. Opinions can never be wrong. They may not fit, or one may not like them. In this case abstain is the way to respond. The only useful voting on Meta are upvotes to show support. It's like with any ballot. You ain't get to vote for a candidate and against others at the same time - the results would be ridicoulus, like they are on meta.
Some education needs to be done.