Below my quick comments/questions related to few different posts from this thread. Btw - it looks like my poll definitely misses 6800/6809, as these architectures were mentioned number of times here.
The storybarrym95838 wrote:
> I bought a book about 35 years ago that sampled several different 16-bit
> microprocessors, giving a large chapter to each one and providing
> architecture info and assembly code examples. I think that it covered
> the 8086, 68000, 16000 (later renamed to 32000), 9900, and pdp-11.
>
> I was reading the chapter on the pdp-11, and had reached the detailed
> description of the addressing modes. My friend was sitting nearby, and
> suddenly asked if I was crying. I actually was, a little bit, proving
> beyond a shadow of a doubt that I was a true nerd.
>
> Mike B.
Thanks so much for quoting this story, Barry. I found it touching and poetic and it just proves that being a nerd does not necessarily mean (as some may think) being unhumanistic. Btw - do you have an idea what book that story may be referring to?
68k and PDP-11Chromatix wrote:
68K and PDP-11 can arguably be considered together, as the latter inspired the design of the former. Both were explicitly designed to be friendly to hand-coding assembler.
Oh - I didn't know about that inspiration and you made me curious about it, although a quick search didn't give me many details, aparat a short statement on Wikipedia. I found, though, one interesting comment (by Antron Argaiv) on Hackaday under
A PDP-11 on A Chip article (interesting on its own):
Quote:
Motorola 68000 had a lot of similarities to the PDP-11 (paird A & D registers, auto-increment/decrement, etc).
I talked to a Moto sales rep who said that some of the designers had liked these features of the 11 so much , they included them.
Remember, at the time the 68000 was designed, DEC was donating or selling at a discount, a LOT of 11’s to colleges and universities under the assumption that if you did your assembly language course on an 11, you would be predisposed to buy them when you got into industry…
Based on this thread I see there are some on this Forum with hands-on experience on both platforms. I'm curious your opinions.
Instruction schedulling resman wrote:
For me, it really comes down to instruction scheduling. Being able to hold most of the instruction set and cycle counts in my head (harder and harder the older I get!) is key to "human friendly" assembly programming. I think the 6502 is tops in that category. But other 8 bitters fall into line pretty well.
I see the point and it makes lot of sense to me. I'd also add number of registers that fit in "cognitive capacity" of a human being. But 65xx family, with a single usable rigister drives into ZP trickery and - in my opinion - reduces the friendliness of that (overal friendly) architecture. I remember moving from 65xx to 68k and the feeling of "freedom" it gave me.
RISC-V drogon wrote:
all I need to do now is find the right RISC-V platform to use which may well end up being an FPGA but that's for another place...
(...)
I've seen many - the issue is that broadly speaking they fall into 2 categories: One is the "microcontroller" types - a few 100 KB of flash and a few 10s of K of RAM... OR many MB -> GB of RAM, 64-bit, multi-core designed for Linux. There are very few ones in the range I want for a hobby project - so that same few 100KB of Flash but 0.5 to 1MB of RAM and easy to use peripherals. Everyone wants to cram as much as possible, so you end up with Wi-Fi, AI, Encryption, USB systems on the chip which then makes it as hard to write a bare-metal thing from scratch for as the Raspberry Pi (Which I have done).
I'm getting the point, especially in the context od moving your '816 project to RISC-V platform. Some little, simple computer (not a microcontroller) would make a lot of sense here. I'm curious whether you've found something that matches your criteria. Looks like some of the Forum members are interested in that architecture, so would be good to know about some good platform to try (a topic for a separate thread, though).