ah, PDE/PTE A/D writes... what a source of variety over the decades!
some chips set them step by step, as shown in the article
others only set them at them very end, together
and then there are chips which follow the read-modify-write op with another read, to check if the RMW succeeded... which promptly causes them to hang hard when the page tables live in read-only memory i.e. ROM... fun fun fun!
as for segmentation fun... think about CS always being writeable in real mode... even though the access rights only have a R but no W bit for it...
It used segmented 32-bit mode. Flat mode doesn’t support virtual addressing which was accomplished with the descriptor tables (and the ES register) if I recall correctly. lol it’s been 33 years since I wrote windows drivers. Had to use masm to compile the 16-bit segments to thunk to the kernel
some chips set them step by step, as shown in the article
others only set them at them very end, together
and then there are chips which follow the read-modify-write op with another read, to check if the RMW succeeded... which promptly causes them to hang hard when the page tables live in read-only memory i.e. ROM... fun fun fun!
as for segmentation fun... think about CS always being writeable in real mode... even though the access rights only have a R but no W bit for it...