4 ms·

> compared to more complex and more expensive CPUs like the Z80 It preceded the Z80 by a year or two.

vidarh 5y ago
Yes, but that wasn't really the point. The 65xx series was a result of Chuck Peddle initially proposing a drastically cost-cut design similar to the 68xx series from Motorola. When Motorola didn't want to do it, Peddle and other Motorola staff left for MOS Technologies to realise the design. So the simplicity of the 65xx had less to do with when it was released than with an explicit design goal to be extremely simple and cheap.
- masswerk 5y ago
  Is there more on this proposal (e.g., a preserved document)? Something I found especially interesting is the decision to not implement "STX abs,Y" and "STY abs,X", while the decoding matrix would have easily provided for this. Was this to keep the instruction set arbitrarily simple (as in explicitly not orthogonal)? Or was there a more serious architectural conflict? Or was this just a legacy from the 6800, which had just a single index register, thus lacking a similar option? (I added a note on this to the article.)
  - vidarh 5y ago
    Most of what I know about that comes from Brian Bagnall's books (e.g. Commodore: A company on the edge). It's covered in the first chapter. I don't know of any preserved documents - if they exist they'd belong to Motorola, and I'd expect the leavers would have preferred to ditch any such documents (though part of the reason for the settlement with Motorola was that one of the engineers stupidly taking 6800 documentation with him). This [1] summarizes it. Here [2] is an interview by Computer History Museum of Chuck Peddle. It matches up with the first chapters in Bagnalls book very closely. From about 50 minutes in he talks about his meetings w/Motorola customers that told him the 6800 was too expensive. From about 58m in they talk about basically setting a size metric for the chip to meet a low enough price point. So the starting point was what they could fit in small enough space. You might also like the Computer History Museum interview w/Bill Mensch [3] [1] http://www.cpushack.com/2013/08/03/mos-technology-mcs6501-processor/ http://www.cpushack.com/2013/08/03/mos-technology-mcs6501-pr... [2] https://www.youtube.com/watch?v=enHF9lMseP8 https://www.youtube.com/watch?v=enHF9lMseP8 [3] https://www.youtube.com/watch?v=Ne1ApyqSvm0 https://www.youtube.com/watch?v=Ne1ApyqSvm0
    - masswerk 5y ago
      Thanks! I'll have a closer look at these. – Admittedly, I haven't looked deep into Chuck Peddle's history (besides anything related to the PET), yet.

Yes, but that wasn't really the point. The 65xx series was a result of Chuck Peddle initially proposing a drastically cost-cut design similar to the 68xx series from Motorola. When Motorola didn't want to do it, Peddle and other Motorola staff left for MOS Technologies to realise the design. So the simplicity of the 65xx had less to do with when it was released than with an explicit design goal to be extremely simple and cheap.

masswerk 5y ago
Is there more on this proposal (e.g., a preserved document)? Something I found especially interesting is the decision to not implement "STX abs,Y" and "STY abs,X", while the decoding matrix would have easily provided for this. Was this to keep the instruction set arbitrarily simple (as in explicitly not orthogonal)? Or was there a more serious architectural conflict? Or was this just a legacy from the 6800, which had just a single index register, thus lacking a similar option? (I added a note on this to the article.)
- vidarh 5y ago
  Most of what I know about that comes from Brian Bagnall's books (e.g. Commodore: A company on the edge). It's covered in the first chapter. I don't know of any preserved documents - if they exist they'd belong to Motorola, and I'd expect the leavers would have preferred to ditch any such documents (though part of the reason for the settlement with Motorola was that one of the engineers stupidly taking 6800 documentation with him). This [1] summarizes it. Here [2] is an interview by Computer History Museum of Chuck Peddle. It matches up with the first chapters in Bagnalls book very closely. From about 50 minutes in he talks about his meetings w/Motorola customers that told him the 6800 was too expensive. From about 58m in they talk about basically setting a size metric for the chip to meet a low enough price point. So the starting point was what they could fit in small enough space. You might also like the Computer History Museum interview w/Bill Mensch [3] [1] http://www.cpushack.com/2013/08/03/mos-technology-mcs6501-processor/ http://www.cpushack.com/2013/08/03/mos-technology-mcs6501-pr... [2] https://www.youtube.com/watch?v=enHF9lMseP8 https://www.youtube.com/watch?v=enHF9lMseP8 [3] https://www.youtube.com/watch?v=Ne1ApyqSvm0 https://www.youtube.com/watch?v=Ne1ApyqSvm0
  - masswerk 5y ago
    Thanks! I'll have a closer look at these. – Admittedly, I haven't looked deep into Chuck Peddle's history (besides anything related to the PET), yet.