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wolfgke | 5 years 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).

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userbinator|5 years 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.

colejohnson66|5 years 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|5 years 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): "[...] 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. [...]"