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I seem to recall Xenix ran on an 80286. Speaking of which, did anyone ever end up apologising for the 80286?

by hoodoof 11y ago

qwertyuiop924 11y ago
Not iirc. But I wasn't around at the time, so nobody told me anything about what was wrong with the 286 in the first place.
- dsr_ 11y ago
  As I recall, it was mostly that backwards-compatibility with 8086 was so required that they put every useful performance enhancement except raw MHz in a separate protected mode... and then you couldn't switch between protected and real mode without (I am not making this up) asking the 8042 processor controlling the keyboard to hold your beer and reset you, which could take an agonizingly long time.
  - Sanddancer 11y ago
    The 8042 had another "fun" function on the 286 too. Because there were a number of poorly written programs that expected the memory to roll over at 0x0FFFFF, in order to maintain compatibility, they needed some way of turning off the A20 line. Now, in order to save money, IBM noticed that there was a spare pin on the 8042 that they used to control whether or not the A20 pin would be held low or not. Now, because this became another bit of needed backward compatibility, a way to assert the A20 pin stuck around until Intel's Haswell line, several decades after A20 gating was needed. Also, there was another way of getting the processor back into real mode that was even more fun. You'd initiate a triple fault to trigger the reset, because that was faster than asking the 8042 to do it for you. Oh, the good old days.
    - rbanffy 11y ago
      I know the PC was designed under a very tight deadline, about a year. I wonder what the hardware team spent the remaining 10 months... Someone should apologize for the whole machine...
  - qwertyuiop924 11y ago
    I heard something about that. Also I heard that the segmented memory was EVIL, or something. Although apparently unixes running on the platform used it to simulate the user/kernel divide. And honestly, we all know that x86 is an awkward architecture at best, hampered by the need for obsessive backwards compatibility, and that without the huge binary footprint, ARM and RISC would have won. Remember when Andrew Tanenbaum said that his issues with Linux's design were a moot point, because we'd all be running HURD on RISC machines by the year 2000? Have you noticed people in the Linux crowd saying that Wayland will kill X? You'd thing we'd have learned our lesson by now: Backwards compatibility trumps all.
- cbd1984 11y ago
  What was wrong with the 80286 was that Intel expected it to be used like processors are used now: Flipped into protected mode once at boot-up and kept there the whole time application software is running.
  - hoodoof 11y ago
    Also it had a 24 bit address space when really the industry was ready for 32 bit and I have a vague recollection that there were other 32 bit CPUs available at that from other manufacturers (maybe Motorola?) but Intel was lagging. The 24 bit address space meant that developers had to deal with some sort of funky segmented addressing scheme I believe that was also a pain on the 8086 and I think a nice flat 32 bit memory space would have been a whole lot better. Bill Gates called the 80286 "brain dead". I seem to recall it being effectively a faster 8086 but its extra capabilities were both underpowered and impractical to use.

I seem to recall Xenix ran on an 80286. Speaking of which, did anyone ever end up apologising for the 80286?

by hoodoof 11y ago

I seem to recall Xenix ran on an 80286. Speaking of which, did anyone ever end up apologising for the 80286?

Not iirc. But I wasn't around at the time, so nobody told me anything about what was wrong with the 286 in the first place.

dsr_ 11y ago
As I recall, it was mostly that backwards-compatibility with 8086 was so required that they put every useful performance enhancement except raw MHz in a separate protected mode... and then you couldn't switch between protected and real mode without (I am not making this up) asking the 8042 processor controlling the keyboard to hold your beer and reset you, which could take an agonizingly long time.
- Sanddancer 11y ago
  The 8042 had another "fun" function on the 286 too. Because there were a number of poorly written programs that expected the memory to roll over at 0x0FFFFF, in order to maintain compatibility, they needed some way of turning off the A20 line. Now, in order to save money, IBM noticed that there was a spare pin on the 8042 that they used to control whether or not the A20 pin would be held low or not. Now, because this became another bit of needed backward compatibility, a way to assert the A20 pin stuck around until Intel's Haswell line, several decades after A20 gating was needed. Also, there was another way of getting the processor back into real mode that was even more fun. You'd initiate a triple fault to trigger the reset, because that was faster than asking the 8042 to do it for you. Oh, the good old days.
  - rbanffy 11y ago
    I know the PC was designed under a very tight deadline, about a year. I wonder what the hardware team spent the remaining 10 months... Someone should apologize for the whole machine...
- qwertyuiop924 11y ago
  I heard something about that. Also I heard that the segmented memory was EVIL, or something. Although apparently unixes running on the platform used it to simulate the user/kernel divide. And honestly, we all know that x86 is an awkward architecture at best, hampered by the need for obsessive backwards compatibility, and that without the huge binary footprint, ARM and RISC would have won. Remember when Andrew Tanenbaum said that his issues with Linux's design were a moot point, because we'd all be running HURD on RISC machines by the year 2000? Have you noticed people in the Linux crowd saying that Wayland will kill X? You'd thing we'd have learned our lesson by now: Backwards compatibility trumps all.
cbd1984 11y ago
What was wrong with the 80286 was that Intel expected it to be used like processors are used now: Flipped into protected mode once at boot-up and kept there the whole time application software is running.
- hoodoof 11y ago
  Also it had a 24 bit address space when really the industry was ready for 32 bit and I have a vague recollection that there were other 32 bit CPUs available at that from other manufacturers (maybe Motorola?) but Intel was lagging. The 24 bit address space meant that developers had to deal with some sort of funky segmented addressing scheme I believe that was also a pain on the 8086 and I think a nice flat 32 bit memory space would have been a whole lot better. Bill Gates called the 80286 "brain dead". I seem to recall it being effectively a faster 8086 but its extra capabilities were both underpowered and impractical to use.