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Discussion on: Why is 32-bit called x86 and not x32?

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tobiassn profile image
Tobias SN

You say that the 386 was the first 32-bit x86 processor, but wasn’t Protected Mode (32-bit mode) introduced in the 286?

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alphaolomi profile image
Alpha Olomi Author

True but also 286 was 16-bit microprocessor at first

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tobiassn profile image
Tobias SN

You mean by default? Every x86 processor is like that for compatibility purposes.

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jeroen1205 profile image
Jeroen Jacobs • Edited on

No, the 286 had a Protected Mode, but it was not 32-bit. It was actually a 24-bit addressing mode which allowed access to 16MB of RAM.

Since the 286 was strictly a 16bit processor, it used segmentation even in Protected Mode. The segment register was loaded with a 16-bit index, which pointed to an entry in a descriptor table. This entry contained the actual 24bit base address.

If this sound complicated to you, you are right, it is. 286 Protected Mode was barely used. You were still restricted to 64Kb addressing within that one segment.

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tobiassn profile image
Tobias SN

Huh. I read that Protected Mode was introduced with the 286, and just assumed that it meant that the 286 was 32-bit. Thanks for the clarification.