Booting to the hard drive from a floppy

[inflater]

Hi,
Try this:

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jmp far 0x0000:0x7C00

-or-

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xor ax,ax
mov ds,ax
jmp far [ds:7C00h]

-or-

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cli
xor ax,ax
mov bx,7C00h
push ax
push bx
sti
retf

I wonder why that INT 19h is not working for you, as borrowed from Ralph Brown's interrupt list, it should work.
I will test it in my OS and I'll post my results.

//EDIT: Your right my man, INT 19h is not working with that...

Regards,
inflater

[fbelzile]

The first code didn't compile.
The second code compiled but didn't work.
The third code WORKED like a charm!

Thank-you:

XCHG figured out I had CX as 0000.
Urxae posted the original code that I edited and used.
Inflater mentioned int 19 and solved my jumping problem

Thanks again, I learned lots! Have a great day

[Combuster]

Some notes:

jmp far 0x0000:0x7C00

I use

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jmp 0x0000:0x7C00

(i.e. without the far) which assembles correctly.

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xor ax,ax
mov ds,ax
jmp far [ds:7C00h]

this is obviously wrong. Note the memory operand - it will try to load the offset from memory at 0x0:0x7c00 not jump to 0x0:0x7c00

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cli
xor ax,ax
mov bx,7C00h
push ax
push bx
sti
retf

I don't think the cli/sti pair is necessary here. There is no inconsistent hardware state anywhere in that block so...

[inflater]

I don't think the cli/sti pair is necessary here. There is no inconsistent hardware state anywhere in that block so...

I was setting up segment registers and stack there , fbelzile, if you do this in your kernel, you can safely strip off CLI and STI parts.

inflater