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i really don't think the 6800 begat the 68000 - they have almost nothing in common, architecture-wise. on the other hand, the intel 8080 certainly connected to

i really don't think the 6800 begat the 68000 - they have almost nothing in common, architecture-wise. on the other hand, the intel 8080 certainly connected to the 8086 and in fact a lot of 8086 programs were mechanically translated, at least in part, from the 8080 (and z80).

ggm 3y ago
Look I get this, its not like one is backwards compatible to the other. But the 68000 exists because Motorola were invested in the 6800 and saw a path onward, albiet leapfrogging to 32 bits, and deliberately not doing backwards compat ISA. Intel and Zilog took another path. Their path in some ways, was the wiser course because IBM jumped on the Intel model and .. here we are. Zilog couldn't make it work as well for them as Intel did.
- Tor3 3y ago
  I don't really get that. The 6800 begat the 6809, and that was the connection to the 6800. When Motorola made the 68000 they decided to begin with a clean slate, there's really nothing in connection with the 6800 except the numbering scheme and both being big endian. If you want to use the word 'begat' then it fits Intel much more. Intel made the 8086, and Mensch made the 65816, both went for backwards compatibility (source or architecture) to some extent (which gave us segments and other negative artifacts). So yes we agree on the facts, it's just so strange that you in your previous post said that the "6800 begat the 68000" - if anything, it didn't. All the companies went ahead with 16- and / or 32-bit CPUs, the difference is that Motorola broke away from their 8-bit past while doing so.
  - zozbot234 3y ago
    > the difference is that Motorola broke away from their 8-bit past while doing so. And then they did it again with the PowerPC (and the 88000 prior to that) which had very little in common with the 68k.
adrian_b 3y ago
They actually have many details in common, including some suboptimal choices, like the handling of the flags, but those are not due to 68000 being derived from 6800, as there was no such direct connection, but due to the fact that both the 6800 and the 68000 ISAs have been strongly influenced by the DEC PDP-11, which was the most popular minicomputer during the seventies. Due to very similar mnemonics, the assembly languages of MC6800 and of MC68000 resemble even more the PDP-11 assembly language than their actual instruction sets.

ggm 3y ago

Look I get this, its not like one is backwards compatible to the other. But the 68000 exists because Motorola were invested in the 6800 and saw a path onward, albiet leapfrogging to 32 bits, and deliberately not doing backwards compat ISA. Intel and Zilog took another path. Their path in some ways, was the wiser course because IBM jumped on the Intel model and .. here we are. Zilog couldn't make it work as well for them as Intel did.

Tor3 3y ago
I don't really get that. The 6800 begat the 6809, and that was the connection to the 6800. When Motorola made the 68000 they decided to begin with a clean slate, there's really nothing in connection with the 6800 except the numbering scheme and both being big endian. If you want to use the word 'begat' then it fits Intel much more. Intel made the 8086, and Mensch made the 65816, both went for backwards compatibility (source or architecture) to some extent (which gave us segments and other negative artifacts). So yes we agree on the facts, it's just so strange that you in your previous post said that the "6800 begat the 68000" - if anything, it didn't. All the companies went ahead with 16- and / or 32-bit CPUs, the difference is that Motorola broke away from their 8-bit past while doing so.
- zozbot234 3y ago
  > the difference is that Motorola broke away from their 8-bit past while doing so. And then they did it again with the PowerPC (and the 88000 prior to that) which had very little in common with the 68k.

adrian_b 3y ago

They actually have many details in common, including some suboptimal choices, like the handling of the flags, but those are not due to 68000 being derived from 6800, as there was no such direct connection, but due to the fact that both the 6800 and the 68000 ISAs have been strongly influenced by the DEC PDP-11, which was the most popular minicomputer during the seventies. Due to very similar mnemonics, the assembly languages of MC6800 and of MC68000 resemble even more the PDP-11 assembly language than their actual instruction sets.