Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!uccba!uceng!ndcheg!ndmath!cww
From: cww@ndmath.UUCP (Clarence W. Wilkerson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: ROMable code continued
Summary: The id bytes and checksum
	 of a rom
Message-ID: <1262@ndmath.UUCP>
Date: 30 Dec 88 20:29:58 GMT
References: <88Dec27.173804est.2417@godzilla.eecg.toronto.edu>
Distribution: na
Organization: Math. Dept., Univ. of Notre Dame
Lines: 15


These requirements are to allow the main bios roms to link in
other roms. It does this by calling the initialization routine
in the rom with correct id and checksum. This routine is responsible
for setting up its interrupt vectors, etc, so that it can be accessed
indirectly by "ROM BIOS calls". For example, a disk controller ROM
might steal interrupt 14 hex, and intercept each call to decide if
it can use the winchester or pass it on the bios floppy code.
   Actually, your initialization code can do anything it wants,
   including not returning to the calling routine. However, I have
   not been able to determine the initialization sequence as to when the
   keyboard, console drivers, etc are initialized, so the results have varied
   from machine to machine. I included in a winchester ROM code to ask for a password. On some machines, this worked. On others, the keyboard was not
   set yet, so it all frooze.
   "froze"