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A comment on The 640K memory limit of MS-DOS. Parent comment

Re:The 640K memory limit of MS-DOS by phicoh on Saturday June 09, 2018 @05:56PM (#17275258)
On a 286 you do not have access to real mode when in protected mode. You need a 386 for that.

A crazy trick that did work is to cause a triple fault in protected mode. That would reset the 286. Then there was a little bit of support from the BIOS. You could tell the BIOS to not run the power on self tests and load the MBR from disk. Instead the BIOS would jump to a specific memory location.

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Re:The 640K memory limit of MS-DOS by wolfgke on Sunday June 10, 2018 @07:47AM (#17277665)
> On a 286 you do not have access to real mode when in protected mode. You need a 386 for that.

I think that you are mistaken: I am rather sure that the undocumented LOADALL instruction could make something like that possible:

> https://en.wikipedia.org/wiki/LOADALL

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Re:The 640K memory limit of MS-DOS by wolfgke on Sunday June 10, 2018 @02:01PM (#17279309)
Update: Indeed it is possible to use LOADALL to switch from protected mode to real mode:

> http://www.os2museum.com/wp/loadall-strikes-again/

Article found via https://retrocomputing.stackexchange.com/a/220/4889

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Re:The 640K memory limit of MS-DOS by yuhong on Friday June 15, 2018 @09:09PM (#17325148)
No it is not, the article was later corrected.
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Re:The 640K memory limit of MS-DOS by yuhong on Saturday June 16, 2018 @02:31AM (#17326207)
Correct link BTW: http://www.os2museum.com/wp/will-the-real-real-mode-please-s...
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