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Nightloader/i386/legacy-boot/src-asm/memory/a20.asm

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Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
; A20 Wraparound check as gotten from osdev.org
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
check_a20_wraparound:
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
pushf
push ds
push es
push di
push si
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
xor ax, ax ; ax = 0
mov es, ax
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
not ax ; ax = 0xFFFF
mov ds, ax
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
mov di, 0x0500
mov si, 0x0510
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
mov al, byte [es:di]
push ax
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
mov al, byte [ds:si]
push ax
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
mov byte [es:di], 0x00
mov byte [ds:si], 0xFF
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
cmp byte [es:di], 0xFF
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
pop ax
mov byte [ds:si], al
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
pop ax
mov byte [es:di], al
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
mov ax, 0
je .exit
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
mov ax, 1
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
Fix A20 by copying others' implementation The implementation of the A20 wraparound check was off in some way, which is why the new implementation was copied from osdev.org, just using minor modifications to the label naming.
2024-08-06 11:25:42 +00:00
.exit:
pop si
pop di
pop es
pop ds
popf
Add A20 line check This commit adds a check for whether the A20 line is usable; checking whether more than one megabyte of RAM can be used. If it isn't usable, it currently isn't activated, but rather, the boot process is stopped.
2024-06-16 21:02:55 +00:00
ret