While I agree about the 6800 being cumbersome in some respects, it was still used, not only in the Altair 680B or the SWTPC (checking Wikipedia: Also the Tektronix 4051 computer). But maybe the derivatives of the 6800 is where the real use was. The TU80 and TU81 (DEC tape drives) I remember from the top of my head. They used the 6802 variant, with 128 bytes of built-in RAM. I've also seen the 6800 original used in other peripherals here and there. So the 6800 family (leaving out the real fix - the 6809) ended up mainly in the market Chuck Peddle had in mind for the 6502, he apparently didn't imagine a personal computer revolution involving the 6502. As for the 6800, even though it's no 6502, I suspect that the total number of 6800-compatible CPUs sold over the years was quite large. The legacy of the 6800 (and its support chips) shouldn't be underestimated. The 1-index register variant managed to live on as the 68HC05 for some time, although the 68HC11 did better (and is still used) with two index registers (but otherwise instruction compatible with the 6800).

The 6501/6502 was all about saving silicon, to be able to sell the chip at less than a tenth of the going price for CPUs at the time ($360 according to Wikipedia). Motorola didn't believe in that approach, which is why Peddle&Co left. So the design choices for the 6501/6502 was more about saving silicon, and doing the best of what was left, than about an optimal design seen from a programmer's point of view. But they did put some effort into getting very fast interrupts, and all in all I think the 6502 did exceedingly well with what could be done with the available silicon.
As for compilers, remember that FORTRAN (and COBOL!) had been around since the fifties, and you could run FORTRAN in 4K on late sixties/early seventies minis. So maybe the memory cost wasn't really why the CPU wasn't designed for compilers (if that was indeed the case), but maybe more the PDP-11 idea[*] - that it should be easy, or even delightful, to program in assembly code.

[*](Although there were earlier architectures with a similar idea, just not as well known as the PDP-11)

I think that when they first designed the 65xx series, they didn't really plan on anyone using high level languages. It wasn't intended to be a microcomputer processor.

The micro-computer didn't really exist at that time, so it seems unlikely that the 6502 was designed to be used in a micro-computer. The Altair-8800 was available, but it was a kit. Also, it would be quite a few years before the micro-computer would be used for anything other than playing video games or writing educational programs in line-number BASIC (by "educational" I mean: "useless").

One big virtue of the 6502 (other that low cost) was low interrupt latency --- this seems to imply that it was intended to be used as a micro-controller --- micro-computers are not real-time, so it doesn't really matter how fast they do I/O.

Anyway --- given a time-machine, I think my suggestions would have changed the course of history.

I also think that the desire for backward-compatibility screws up progress most of the time. At the time that the 65c02 came out, it was not too late to take my suggestions, although dropping indirect-X would have killed backward-compatibility --- all in all, the 65c02 was too conservative, offering only very minor improvement over the 6502 for programmers (reduced power consumption was its only real improvement, which is only an issue in micro-controllers) --- this opportunity to make a big leap forward was lost...

In Abrash's Zen book, he had a chapter titled: "Strange Fruit of the 8080." That has really been the hallmark of the computer business --- a lot of "strange fruit" resulting from the desire to maintain backward-compatibility with obsolete technology.

If you used a time machine to make suggestions that they heeded, you wouldn't need a time machine to go back and make suggestions, etc etc etc.

Yes, Peddle had industrial use in mind for the design. He didn't imagine the Apple II, the PET, the Commodore 64. But then again, few did.

Not sure what you mean by 'not real-time', because of course microcomputers can do RT. RT only means that an event can be handled inside a given time constraint, and micros can do that very well, in particular the early ones which were bare-metal, with no OS. Most of my projects using an Apple II back in the day were real-time, e.g. real-time control of a programmed satellite-tracking system.

I can only agree with that. I've seen a few examples of keeping compatibility which didn't hamper progress (and in one case, a company managing the trick of keeping compatibility in one of their product lines, with great success, and introducing a new product with no ties to the old one, but with a design which could never progress w.r.t. performance. But that's an exception. Acorn came up with the ARM instead of trying for compatibility with earlier products. That went pretty well.)

Too bad it didn't go well for Acorn.

Well, I don't know about that - Acorn had another 13 or 14 years in them after the ARM1 chip came back working, and many people you would have thought of as Acorn people became ARM people. They must have sold a lot of Archimedes and RiscPC machines. Today, RISCOS remains quite active, and stardot is a very active forum. You could easily argue Acorn's legacy is as substantial as WDC's, even though WDC are still going. You could easily argue that we wouldn't have the Raspberry Pi without Acorn.

Of course, if you care mostly about Acorn's continued existence and the future of the Phoebe project, it does indeed look like it didn't go well.

Having been in electronics in the days before the genesis of the MC6800 and MOS6501/6502, I can tell you with some authority that industrial process control was a major target of early microprocessors. If you had been around that stuff in those days you would have been working with gobs of relays or hundreds of 74xx discrete devices. The microprocessor was a huge leap forward in designing intelligence into machines, since it consolidated so much logic into a single piece of hardware. MOS Technology's genius wasn't so much in the MPU itself as was in the recognition of the need for a low-cost device with good performance that was easy to design into a system and (relatively) easy to program.


The earliest microcomputers were most definitely real time devices. They either had no operating system whatsoever or a very rudimentary one that didn't get in the way of meeting the strict processing deadlines that are characteristic of R/T environments, including the need to get unencumbered register-level access to I/O hardware. I knew of several real time applications that were run on a Commodore 64 that easily handled the required processing. Although the C-64 was a fairly advanced computer as eight bit machines went, it fully exposed all hardware to the assembly language programmer, even to the point of allowing the programmer to map out all ROM and leave only RAM and I/O devices exposed (only locations $0000 and $0001 are immutable). That's pretty bare metal by any measure and was very conducive to setting up a real time environment.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

I know you meant that those locations' configuration in the memory mapping are immutable, but just for spits & shingles the off-CPU RAM bytes themselves are mutable as well.

Any 6510 write to those address locations issues an addressed write on the bus, but leaves the data pins tristated. In this case, the data bus values will generally still retain the value the VIC-II read in the last bus edge, so it can be timed to write a specific byte to those addresses. Reading RAM under 00/01 can be done by pointing the screen there and using sprite collisions.

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WFDis Interactive 6502 Disassembler
AcheronVM: A Reconfigurable 16-bit Virtual CPU for the 6502 Microprocessor

Yes, that is the time-machine paradox.

Another problem is that they are unlikely to heed my suggestions --- nobody listens to me in the present, so why would I expect anything different if I were to magically appear in the 1970s?

Very good point, especially because: You look, act, and talk like someone from 2016. Your memory and knowledge of the 1970s has been affected by all the over-exaggeration of the way things were then, in all the modern TV and movies about that era. So even if you try to fit in, you'll look like a weirdo.

Wasn't there a Bread lyric about time travel?

Maybe time-machines do exist --- I'm actually from the 1970s and I travelled ahead to 2016 --- that is why I look like a weirdo (I don't even own a smart-phone; how weird is that?).

I did too, just at a pretty slow pace (sure doesn't seem like it in retrospect!) but I did get several smartphones!

I hope to travel to 2017 in a few weeks.

Holy s**t!! ... I thought I was the only weird looking dude younger than 65 who could afford a smart phone but never bought one.

Mike B.

I don't use a smartphone. I don't like what they've done to society. I told this to a friend, and he replied, "I'm ahead of you there—I don't like society!" (although he uses a smartphone and a tablet). I also don't want the radiation. I have many hours of lecture bookmarked on the computer, with tons of very convincing study results showing how much damage the radiation is slowly doing to human health. The industry tries desperately to discount it though, since it would wipe out their business. I mostly use a desktop PC with a nice big monitor and a wired internet connection, followed by occasionally my laptop, and I carry an old flip phone just for emergencies and it may go a month at a time without even getting turned on. (I mainly use the landline phone on my desk for phone service.)

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?