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Comment by colejohnson66 | Hacker News Reader

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).

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> (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).

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”?

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): "[...] 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. [...]"

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.

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.

Yeah, but what about servers and data enters?

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.

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