4 ms·

The problem was mainly in x86, existing code already mostly used instructions that belonged to the fast subset, and on 68k, it didn't. So while you could evolve

The problem was mainly in x86, existing code already mostly used instructions that belonged to the fast subset, and on 68k, it didn't. So while you could evolve the instruction set towards a saner design (and the 68060 was well on the way towards that), only new code would benefit from it.

Someone 11mo ago
> only new code would benefit from it. Not only new code. Old code in an high-level language would benefit, too, if the language compiler was updated and the code recompiled.
- actionfromafar 11mo ago
  Or sometimes, binary pached.
  - Findecanor 11mo ago
    This. Don't underestimate the amount of M68K code written in assembly language.
- fredoralive 11mo ago
  Not everyone has that sort of luxury of access to source etc., people want their existing binaries to run faster. Also, if you need to recompile to get a performance boost, why not recompile for a cleaner modern architecture? You can always use an emulator for legacy code, if it isn't going to run fast on a modern CPU either way...
robinsonb5 11mo ago
And of course that's exactly what they did with Coldfire - rounding off the inconvenient corners of the ISA to produce CPUs with lower power requirements and able to run at higher clock speeds.
- kjs3 11mo ago
  They did it with the 68030 before Coldfire. They discarded a number of things (e.g. addressing modes) that seemed like good ideas for the <=68020 but didn't end up being used in practice.
fch42 11mo ago
on the m68k, the "cisc-y-ness" is in the many many addressing modes, whereas x86 in that particular aspect of the architecture has always been rather "risc-y" (read: rather limited compared to other CISC architectures, including m68k). The core instruction set of the m68k, as far as ALU/FPU is concerned, is simple enough. But converting the addressing modes to "risc building blocks" (μops or whatever term you like to use) is harder.

Someone 11mo ago

> only new code would benefit from it. Not only new code. Old code in an high-level language would benefit, too, if the language compiler was updated and the code recompiled.

actionfromafar 11mo ago
Or sometimes, binary pached.
- Findecanor 11mo ago
  This. Don't underestimate the amount of M68K code written in assembly language.
fredoralive 11mo ago
Not everyone has that sort of luxury of access to source etc., people want their existing binaries to run faster. Also, if you need to recompile to get a performance boost, why not recompile for a cleaner modern architecture? You can always use an emulator for legacy code, if it isn't going to run fast on a modern CPU either way...

robinsonb5 11mo ago

And of course that's exactly what they did with Coldfire - rounding off the inconvenient corners of the ISA to produce CPUs with lower power requirements and able to run at higher clock speeds.

kjs3 11mo ago
They did it with the 68030 before Coldfire. They discarded a number of things (e.g. addressing modes) that seemed like good ideas for the <=68020 but didn't end up being used in practice.

fch42 11mo ago

on the m68k, the "cisc-y-ness" is in the many many addressing modes, whereas x86 in that particular aspect of the architecture has always been rather "risc-y" (read: rather limited compared to other CISC architectures, including m68k). The core instruction set of the m68k, as far as ALU/FPU is concerned, is simple enough. But converting the addressing modes to "risc building blocks" (μops or whatever term you like to use) is harder.