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> z80 and 8086 were both garbage, next to the 68000. At that time, Z80 and 8088/8086 targeted very different market segments than the 68000. So, this is a quit

> z80 and 8086 were both garbage, next to the 68000. At that time, Z80 and 8088/8086 targeted very different market segments than the 68000. So, this is a quite unfair comparison.

AnimalMuppet 7y ago
OK, the 286 was also garbage compared to the 68000.
- kjs3 7y ago
  I know it's heretical, but the '286 had a bunch of really interesting innovations, like a primitive capabilities based architecture. The big downfall of the '286 was they tried to do the 8086 backward compatibility and completely screwed it up. Ignoring that and writing an OS just for the '286 features was kinda interesting at the time. Not now...but at the time.
- tropo 7y ago
  The 68000 has some serious design flaws in the architecture. A notable one is the autoincrement and autodecrement of indirect memory references. This makes it difficult to get the architecture running instructions in parallel. Memory can be changing, but the address at which it changes is determined late. It gets even more troublesome if the CPU comes with a MMU. It becomes necessary to avoid actually performing the autoincrement or autodecrement until all page faults have been resolved. (getting that VAX feel here) Remember that memory accesses can go to the same location as other memory accesses and/or to memory mapped IO, so simply rolling back the value is no good. The situation with flags wasn't any better than x86 has, which is pretty bad. There are partial flags updates, undefined flag updates, and a mix of math flags with other types of flags. The interrupt situation was bad. The CPU architecture specifies a small number of levels. Better designs, like x86 and PowerPC, leave that up to the interrupt controller chipset.
  - snvzz 7y ago
    >The 68000 has some serious design flaws in the architecture. So do all CPUs from that era. This is why 68000 was replaced by Motorola itself. It's an abnormality x86 has been dragged this far. >The CPU architecture specifies a small number of levels. 7 is pretty reasonable. They're autovectored, so interrupt latency is low. 68000 was often chosen for realtime applications due to this feature. >Better designs, like x86 and PowerPC, leave that up to the interrupt controller chipset. 68000 doesn't in any way prevent having an external interrupt controller. Paula fills that role in the Amiga, providing 15 interrupts, mapped to the autovectored ones.
    - kjs3 7y ago
      In other words: "If I get to define what's good, I always get to be right". Someone who knows a lot more than you disagrees: https://yarchive.net/comp/linux/x86.html https://yarchive.net/comp/linux/x86.html
- snvzz 7y ago
  So were 386, 486 and Pentium. At that time (Pentium), 68060 (which was also superscalar and released months earlier) would easily beat Pentium's performance at half the clock and much lower power. Later on, x86 would surpass 68000 series, but only because Motorola never released a 68k successor for 68060. They moved on to PowerPC.
  - kjs3 7y ago
    Yes, the 68060 was pretty nifty, but no...Motorola moved on to the 88000, which was also very nice. Only then did they dump the 88k and gamble that joining IBM and Apple on the PPC would result in a bigger market to take on Intel. They were wrong.

> z80 and 8086 were both garbage, next to the 68000. At that time, Z80 and 8088/8086 targeted very different market segments than the 68000. So, this is a quite unfair comparison.

AnimalMuppet 7y ago

OK, the 286 was also garbage compared to the 68000.

kjs3 7y ago
I know it's heretical, but the '286 had a bunch of really interesting innovations, like a primitive capabilities based architecture. The big downfall of the '286 was they tried to do the 8086 backward compatibility and completely screwed it up. Ignoring that and writing an OS just for the '286 features was kinda interesting at the time. Not now...but at the time.
tropo 7y ago
The 68000 has some serious design flaws in the architecture. A notable one is the autoincrement and autodecrement of indirect memory references. This makes it difficult to get the architecture running instructions in parallel. Memory can be changing, but the address at which it changes is determined late. It gets even more troublesome if the CPU comes with a MMU. It becomes necessary to avoid actually performing the autoincrement or autodecrement until all page faults have been resolved. (getting that VAX feel here) Remember that memory accesses can go to the same location as other memory accesses and/or to memory mapped IO, so simply rolling back the value is no good. The situation with flags wasn't any better than x86 has, which is pretty bad. There are partial flags updates, undefined flag updates, and a mix of math flags with other types of flags. The interrupt situation was bad. The CPU architecture specifies a small number of levels. Better designs, like x86 and PowerPC, leave that up to the interrupt controller chipset.
- snvzz 7y ago
  >The 68000 has some serious design flaws in the architecture. So do all CPUs from that era. This is why 68000 was replaced by Motorola itself. It's an abnormality x86 has been dragged this far. >The CPU architecture specifies a small number of levels. 7 is pretty reasonable. They're autovectored, so interrupt latency is low. 68000 was often chosen for realtime applications due to this feature. >Better designs, like x86 and PowerPC, leave that up to the interrupt controller chipset. 68000 doesn't in any way prevent having an external interrupt controller. Paula fills that role in the Amiga, providing 15 interrupts, mapped to the autovectored ones.
  - kjs3 7y ago
    In other words: "If I get to define what's good, I always get to be right". Someone who knows a lot more than you disagrees: https://yarchive.net/comp/linux/x86.html https://yarchive.net/comp/linux/x86.html
snvzz 7y ago
So were 386, 486 and Pentium. At that time (Pentium), 68060 (which was also superscalar and released months earlier) would easily beat Pentium's performance at half the clock and much lower power. Later on, x86 would surpass 68000 series, but only because Motorola never released a 68k successor for 68060. They moved on to PowerPC.
- kjs3 7y ago
  Yes, the 68060 was pretty nifty, but no...Motorola moved on to the 88000, which was also very nice. Only then did they dump the 88k and gamble that joining IBM and Apple on the PPC would result in a bigger market to take on Intel. They were wrong.