[OpenBIOS] Summary: Booting the OS

[Jim Stewart]

Chris Arguin wrote:
> 

> Off-the-wall idea #132: How much legacy BIOS support do we really need
> *just* to boot DOS to the point that it loads config.sys and/or
> autoexec.bat? If we supported just that much, and then had a program you
> ran (first) in DOS that basically put a legacy BIOS in as if the real
> BIOS had been shadowed, then we have the best of both worlds. A great BIOS
> with that supports all the nice boot-stuff w/o too much legacy code, but
> available legacy code when you need it for DOS.

I can answer that,

	Int 10h, function Eh		teletype ouput		mostly trivial for serial port
redirect, done for you with most vga cards
	Int 11h				get equipment config	trivial
	Int 12h				mem size		trivial
	Int 13h	 function 0,1,2		disk read write reset	not trivial, probably
don't need write for boot, some dos need funct 8
	Int 16h  function 0,1		keyboard poll and read	mostly trivial for serial
port redirect, don't know about PC keyboard
	Int 1Ah	 function 0,1,2,3	RTC			ok if only stub code to return a valid
constant - must not return nonsense
	Int 19h				Bootstrap		trivial

You also need the adapter scan stuff if you intend to use vga or disk
controllers with on-board bios.

Jim

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