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You mean remove backwards compatibility and ruin the whole reason people use x86? Not to mention that when AMD64 (“long mode”) was introduced, a big amount of c

You mean remove backwards compatibility and ruin the whole reason people use x86? Not to mention that when AMD64 (“long mode”) was introduced, a big amount of cruft was disabled in the new mode (but is still available in 16-bit (“real mode”) and 32-bit (“protected mode”) for compatibility).

wolfgke 6y ago
> (but is still available in 16-bit (“real mode”) and 32-bit (“protected mode”) for compatibility). There exists both 16 bit protected mode (available since the 80286) and 32 bit protected mode (available since the 80386).
- colejohnson66 6y ago
  I thought the 80286 had 32-bit protected mode, but it was badly implemented (the only way to get back to real mode was a reboot), so they fixed it with the 80386. Unless, are you referring to “unreal mode”?
  - cesarb 6y ago
    No, most people forget about it (I had to be reminded by the above comment), but the 80286 did have a 16-bit protected mode. Quoting Wikipedia (https://en.wikipedia.org/wiki/Protected_mode https://en.wikipedia.org/wiki/Protected_mode): "[...] Acceptance was additionally hampered by the fact that the 286 only allowed memory access in 16 bit segments via each of four segment registers, meaning only 4*2^16 bytes, equivalent to 256 kilobytes, could be accessed at a time. [...]"
- userbinator 6y ago
  There is also "32 bit realmode", which is not mentioned in the official documentation but simply a combination of existing states. Ditto for real mode paging and the like --- which finds more applications as emulator acid-tests than anything else.
sroussey 6y ago
Yeah, but what about servers and data enters?
- colejohnson66 6y ago
  If you don’t need backwards compatibility (such as on servers), there’s not much reason to go x86. For that reason, ARM servers exist. IIRC, AWS and Azure have some.
userbinator 6y ago
I am still upset after all this time, at what AMD recklessly did --- out of what might be the same misguided notion as the GP comment, they made instructions like LAHF invalid and removed much of segmentation, only to be forced to put much of it back later because people were actually using them. I suspect Intel was actually working on a more consistent extension to 64 bits too, but AMD beat them to it.

wolfgke 6y ago

> (but is still available in 16-bit (“real mode”) and 32-bit (“protected mode”) for compatibility). There exists both 16 bit protected mode (available since the 80286) and 32 bit protected mode (available since the 80386).

colejohnson66 6y ago
I thought the 80286 had 32-bit protected mode, but it was badly implemented (the only way to get back to real mode was a reboot), so they fixed it with the 80386. Unless, are you referring to “unreal mode”?
- cesarb 6y ago
  No, most people forget about it (I had to be reminded by the above comment), but the 80286 did have a 16-bit protected mode. Quoting Wikipedia (https://en.wikipedia.org/wiki/Protected_mode https://en.wikipedia.org/wiki/Protected_mode): "[...] Acceptance was additionally hampered by the fact that the 286 only allowed memory access in 16 bit segments via each of four segment registers, meaning only 4*2^16 bytes, equivalent to 256 kilobytes, could be accessed at a time. [...]"
userbinator 6y ago
There is also "32 bit realmode", which is not mentioned in the official documentation but simply a combination of existing states. Ditto for real mode paging and the like --- which finds more applications as emulator acid-tests than anything else.

sroussey 6y ago

Yeah, but what about servers and data enters?

colejohnson66 6y ago
If you don’t need backwards compatibility (such as on servers), there’s not much reason to go x86. For that reason, ARM servers exist. IIRC, AWS and Azure have some.

userbinator 6y ago

I am still upset after all this time, at what AMD recklessly did --- out of what might be the same misguided notion as the GP comment, they made instructions like LAHF invalid and removed much of segmentation, only to be forced to put much of it back later because people were actually using them. I suspect Intel was actually working on a more consistent extension to 64 bits too, but AMD beat them to it.