On 01.08.2017 16:49, Peter Stuge wrote:
Note that PM != paging. Neither coreboot nor proprietary BIOS
products used paging traditionally. Ron pushed for paging, there was
a bit of support. I don't know the current situation though.
Also note that PM != "flat real mode" or "32-bit real mode", it's not
really documented as a feature, so I don't know if it has an official
name.
What you do is prepare a GDT with most or all entries having base 0
size 4GB, then enable PM in CR0, ldgdt, set at least cs and ds
(usually more) to the 4GB GDT selectors, then disable PM in CR0 -
*and do not reload cs, ds and other selectors/segment registers*
once back in RM. This then allows 32-bit memory access in RM on 386 up.
Why would I want to address memory in RM with 32 Bits? I don't see any
difference to using PM without Paging enabled.
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