BigDumbDinosaur wrote:
From my perspective, the number of transistors in the 65C816, or the 65C02 for that matter, is a distinctly secondary concern these days. Transistors are cheap....What wasn't cheap was the development time required to figure out how to achieve the desired level of function with a small transistor count. In 2020, development costs continue to override the cost of transistors, even with contemporary design tools.
Sure, but that's a particular hobbyist's perspective, and from a modern point of view, addressing today's concerns and ease of development, the 6502 in its entirety is a complete dead-end path that should be ignored in favour of modern small processor designs. Thinking about the 6502 at all is no more justifiable than thinking about redesigns of the 6502 using the same transistor count as the original NMOS chip. We're all just setting arbitrary limits and goals here for fun, not for efficiency.
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In any case, trying to imitate the NMOS design at the transistor level smacks of agonizing over how to best mount the hand crank on a replica of a Model T Ford.
Which sounds like a pretty valid historical investigation or hobby project to me!
BigEd wrote:
Snial's substantial post brought several things into play...
- the objectives, which should forestall any spurious mention of '816
Well, perhaps we should start by remembering that the post in question itself discussed the '816. Even that aside, I'm with BDD here:
BigDumbDinosaur wrote:
I would not classify mention of the '816 in this context as "spurious...." Plus the 65C816 is a good fit to a C compiler, which fit is being touted by Snial as a primary consideration in the 65T2.
Exactly. If one's examining the design of the 6502 and playing around with a redesign that should allegedly improve it for certain purposes, it makes perfect sense to look at how someone else did it and compare the two new designs. Since the '816 actually appears to meet several of the objectives of Snial's design, it's not only valid to ask, "what are the differences between the two and their effects," but one of the most interesting and educational questions. So I'm pleased to see it raised, though I wouldn't mind a bit more detail on the differences and a deeper investigation of their consequences.
It might also be worth remembering that too much focus on trying to corral discussions into their "correct" places and making sure that people aren't going "off-topic" can be more disruptive to a conversation than just letting it go where it goes. This isn't Wikipedia or a business meeting; especially on topics like this it's more a brainstoming session.
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Looking at it from my perspective, Snial's proposed design, aside from breaking backward compatibility with its predecessors in several ways, has some spurious theories as its foundation. Lacking zero page, what I see is not a 6502-family processor, just something else that has an instruction set that resembles that of a 6502.[/color]
While I agree that the foundational theories seem to have some issues that should be addressed, I suggest that the "zero page," narrowly defined, is not a thing that makes a 6502 a 6502. After all, the 6800 has a zero page as well. I propose that a core feature that gives 6502-nature is actually indirect indexed addressing through a pointer in RAM, which his design perserves, and is why his design is more like a 6502 than the 6800, despite his lacking a zero page and the 6800 having one.