On Thu, 24 Feb 2000, david wrote:
> hi
> my rom dos not auto-start
> i need to write a auto-start rom to swich video cards a startup so far i
> have
>
> d000:0
> dw 0xaa55
> db size
> jmp near start
>
> but i think i have missed a checksum or something
> Thank you
>
> David <sector2@ihug.co.nz>
The size is the amount of code to checksum / 512. It must be at least
1.
Offset 3, the start of initialization code, must not destroy registers:
DS, ES, SS, SP, SI, DI, or BX.
You initialize whatever you want then, after restoring registers,
end with a 'FAR' return.
The checksum is a byte checksum, starts with zero and wraps. The
result is that the entire length of code must checksum to 0.
Contact me via private email if you need more help.
Cheers,
Dick Johnson
Penguin : Linux version 2.3.41 on an i686 machine (800.63 BogoMips).
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This archive was generated by hypermail 2b29 : Tue Feb 29 2000 - 21:00:09 EST