Babystep7: Difference between revisions

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Revision as of 01:33, 10 May 2009 view source osdev>Oros mNo edit summary ← Older edit		Latest revision as of 04:18, 9 June 2024 view source Xtex (talk \| contribs) Interface administrators, Administrators 977 edits m Bot: Replace deprecated source tag with syntaxhighlight
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Line 12: While this code is largely just a party trick, understanding it gives a gentle intro to protected mode concepts and possibly avoids some headaches later on 'cause you skipped over this kind of stuff. The single descriptor in the global descriptor table at the bottom is ~~layed~~laid out to match [[Babystep6\|Babystep6]]. The 'size' given is 1 MB, the base address is 0x0, and the bit fields you can work out yourself. The reason for doing this is to enable 32-bit offsets in real mode. However, you won't be able to go past 1 meg quite yet. Line 22: Finally, note that IP is unaffected by all this, so the code itself is still limited to 64k. <~~source~~syntaxhighlight lang="asm"> AsmExample: Line 34: mov ds, ax ; DS=0 mov ss, ax ; stack starts at 0 mov sp, 0x9c00 ; ~~200h~~2000h past code start cli ; no interrupt Line 72: db 0xAA ;========================================== </syntaxhighlight> ~~</source>~~ ==See Also==