I think the eZ80 was a great expansion of the Z80 but it has the problem that it has no real "protected mode" in the sense that a a Z80-mode program can flip a flag and go into the extended mode without an OS having any veto on it. Since we have so much Z80 software, being able to run it in a box would be great -- practically we can, because old Z80 software had no idea it could flip the flag, but it wouldn't have been had to have some mechanism that would force this transition to be done via a system call... The same is true for 6502 software on a successor architecture and could be true for 65C816 except there isn't so much of it.
The direct page is the gem of the 6502/65C816 addressing modes, extensions should make the most of it.
Also there is no MMU which is something you expect out of a 32-bit machine, but I do think something other than the usual, such as a table of offsets and limits, would be interesting to see.
PaulHoule•4h ago
I think the eZ80 was a great expansion of the Z80 but it has the problem that it has no real "protected mode" in the sense that a a Z80-mode program can flip a flag and go into the extended mode without an OS having any veto on it. Since we have so much Z80 software, being able to run it in a box would be great -- practically we can, because old Z80 software had no idea it could flip the flag, but it wouldn't have been had to have some mechanism that would force this transition to be done via a system call... The same is true for 6502 software on a successor architecture and could be true for 65C816 except there isn't so much of it.
The direct page is the gem of the 6502/65C816 addressing modes, extensions should make the most of it.
Also there is no MMU which is something you expect out of a 32-bit machine, but I do think something other than the usual, such as a table of offsets and limits, would be interesting to see.