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Thanks for sharing this - it's a great interview. I do think there is a subtlety about the 'wasn't intended to compete with the 6800' line though. Chuck Peddl

Thanks for sharing this - it's a great interview. I do think there is a subtlety about the 'wasn't intended to compete with the 6800' line though. Chuck Peddle recognised the market for a much cheaper version of the 6800 which Motorola refused to make, possibly because they couldn't make it that cheaply with the contact lithography process they were using. So Peddle went off to MOS Technology (taking lots of Motorola engineers with him including Mensch) to make the cheaper version. To achieve that goal, they had to cut down on some of the 6800's features. Reducing the size of the stack pointer, only one accumulator, and so on. As it turns out, the end result - the 6501/2 - was actually very competitive with the 6800. So whilst the original intention wasn't to compete with the 6800, in the end it did compete with it very successfully in some important markets. Of course, in addition MOS Technology didn't have the resources of Motorola and so also couldn't compete with them in terms of support, peripherals and so on. Note: I wrote the original post on the 6800 that led to the discussion [1] and I'm now deep in the writing of Part 2 of the 6800 story. (So I've now provided spoilers for Part 2!) [1] https://news.ycombinator.com/item?id=38616591 https://news.ycombinator.com/item?id=38616591

systems_glitch 3y ago
The 6502 absolutely did evolve to compete (and overtake, in some fields) the 6800, no doubt about it! The motivation of competing on the embedded market (whether you see that in Bill Mensch's IEEE interview quote, or Chuck Peddle's lamenting that customers didn't like the $300 tag on the 6800) explains a lot of the design choices though, especially when considering support chips like the 6530 mask-programmed RRIOT. Thanks for a great 6800 writeup, and I look forward to the follow-up! I feel like the 6800 does not get the love it deserves from the current generation of hackers.
- klelatti 3y ago
  Thanks so much! There is so much to cover in Part 2 so it might take a little while. Completely agree that the 6800 needs more love. It was a really important design. PS I'd not seen Mensch's comment that Peddle's intention was to raid Motorola for engineers before - that's an interesting angle!!
  - systems_glitch 3y ago
    Yeah I'm sure the corporate raid had something to do with Motorola dropping the hammer on them over the 6501 pinout. Bill Mensch has said really it was just so they didn't need to design a development system right out the gate, and that they figured other engineers would appreciate that. Seems like it alone wouldn't have been enough to get Motorola mad, especially since they must've known they were just bogging MOS down, and that the pinout wasn't legally defensible reasoning to stop production (MOS and second sources later continued with the 6512, which is effectively 6800 pinout with very, very minor changes).
RetroTechie 3y ago
> As it turns out, the end result - the 6501/2 - was actually very competitive with the 6800. So whilst the original intention wasn't to compete with the 6800, in the end it did compete with it very successfully in some important markets. Another subtlety: the ecosystem. Obviously a cheaper cpu encourages usage in more places. Read: more users & more designers working with it. Over time, that means more tools (including better ones), more OSes to run on it, more application software, more code examples, more existing systems that can be used to kick-start a new design, more knowledge in the field to work around quirks, etc. Often that ecosystem weighs heavier than cpu features, price or performance. Yeah a 'nicer' cpu will drop in price. But by then it's late to the party.
- systems_glitch 3y ago
  That is true, but the 6800 came with a massive ecosystem, all available directly from Motorola! They had reams of useful documentation, including complete, tested implementation guides for things like POS terminals, early simple ECUs, smart disk subsystems, etc. You could build all of those things with chips bought directly from Motorola, engineered to be 100% compatible and easy to interface. For many small systems, you didn't need any non-Motorola parts other than passives. I guess the flip side was, Motorola had to create all that in-house, and the price of the ecosystem reflected that. MOS dumped cheap chips into the world at just the right time and got hobbyists to do the work for free, sometimes with superior results. Probably no one could've seen that coming in 1975.
- imglorp 3y ago
  TFA says the 4040 ~ $29 and 6502 target ~ $20. In a ~ $1300 computer (Apple II, ca. 1977) how price sensitive was that CPU market to $9? The 6800 was ~ $175 in 1974 - that does seem like a clear gulf to the other two. https://en.wikipedia.org/wiki/Motorola_6800 https://en.wikipedia.org/wiki/Motorola_6800
  - klelatti 3y ago
    Not 100% sure I understand your question but if you're asking about 4040 vs 6502 as contenders for Apple II in 1977 - the 4040 was a much more limited design than the 6502 and would not have been viable as the Apple's CPU.

systems_glitch 3y ago

The 6502 absolutely did evolve to compete (and overtake, in some fields) the 6800, no doubt about it! The motivation of competing on the embedded market (whether you see that in Bill Mensch's IEEE interview quote, or Chuck Peddle's lamenting that customers didn't like the $300 tag on the 6800) explains a lot of the design choices though, especially when considering support chips like the 6530 mask-programmed RRIOT. Thanks for a great 6800 writeup, and I look forward to the follow-up! I feel like the 6800 does not get the love it deserves from the current generation of hackers.

klelatti 3y ago
Thanks so much! There is so much to cover in Part 2 so it might take a little while. Completely agree that the 6800 needs more love. It was a really important design. PS I'd not seen Mensch's comment that Peddle's intention was to raid Motorola for engineers before - that's an interesting angle!!
- systems_glitch 3y ago
  Yeah I'm sure the corporate raid had something to do with Motorola dropping the hammer on them over the 6501 pinout. Bill Mensch has said really it was just so they didn't need to design a development system right out the gate, and that they figured other engineers would appreciate that. Seems like it alone wouldn't have been enough to get Motorola mad, especially since they must've known they were just bogging MOS down, and that the pinout wasn't legally defensible reasoning to stop production (MOS and second sources later continued with the 6512, which is effectively 6800 pinout with very, very minor changes).

RetroTechie 3y ago

> As it turns out, the end result - the 6501/2 - was actually very competitive with the 6800. So whilst the original intention wasn't to compete with the 6800, in the end it did compete with it very successfully in some important markets. Another subtlety: the ecosystem. Obviously a cheaper cpu encourages usage in more places. Read: more users & more designers working with it. Over time, that means more tools (including better ones), more OSes to run on it, more application software, more code examples, more existing systems that can be used to kick-start a new design, more knowledge in the field to work around quirks, etc. Often that ecosystem weighs heavier than cpu features, price or performance. Yeah a 'nicer' cpu will drop in price. But by then it's late to the party.

systems_glitch 3y ago
That is true, but the 6800 came with a massive ecosystem, all available directly from Motorola! They had reams of useful documentation, including complete, tested implementation guides for things like POS terminals, early simple ECUs, smart disk subsystems, etc. You could build all of those things with chips bought directly from Motorola, engineered to be 100% compatible and easy to interface. For many small systems, you didn't need any non-Motorola parts other than passives. I guess the flip side was, Motorola had to create all that in-house, and the price of the ecosystem reflected that. MOS dumped cheap chips into the world at just the right time and got hobbyists to do the work for free, sometimes with superior results. Probably no one could've seen that coming in 1975.
imglorp 3y ago
TFA says the 4040 ~ $29 and 6502 target ~ $20. In a ~ $1300 computer (Apple II, ca. 1977) how price sensitive was that CPU market to $9? The 6800 was ~ $175 in 1974 - that does seem like a clear gulf to the other two. https://en.wikipedia.org/wiki/Motorola_6800 https://en.wikipedia.org/wiki/Motorola_6800
- klelatti 3y ago
  Not 100% sure I understand your question but if you're asking about 4040 vs 6502 as contenders for Apple II in 1977 - the 4040 was a much more limited design than the 6502 and would not have been viable as the Apple's CPU.