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From: jwhitnel@csi.UUCP (Jerry Whitnell)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Disabling floppy boot
Message-ID: <1288@csib.csi.UUCP>
Date: Tue, 10-Nov-87 17:04:14 EST
Article-I.D.: csib.1288
Posted: Tue Nov 10 17:04:14 1987
Date-Received: Fri, 13-Nov-87 20:35:42 EST
References: <3543@uw-june.UUCP> <586@bucket.UUCP>
Reply-To: jwhitnel@csib.UUCP (Jerry Whitnell)
Organization: Communications Solutions Inc., San Jose, Ca
Lines: 30

In article <586@bucket.UUCP> leonard@bucket.UUCP (Leonard Erickson) writes:
|Well, we have a Nestar LAN. Somehow the ROM on the network card disables
|the floppy boot. If the network connection is ok, the system will boot
|of the network even if there is a disk in drive A:.
|
|Since the "LAN" looks like a bunch of hard disks to the PC, I'd guess that
|it is using the "hard disk ROM" POST to skip over part of the normal POST.

Actually it doesn't skip over any of the normal POST.  What it does is it
replaces INT 13H (the ROM BIOS disk interrupt) with it's own patch that
redirects I/O for the boot drive to the file server it is booting from.
It also replaces INT 19H which is the interrupt which is the interrupt to
boot the machine, so it gets control before the normal hard disk boot code.
So it goes to the network first, then floppy and harddisk.  I wrote that code
so I think I know how it works :-).

|
|I do know that no modifications of the pc are required. You just drop in
|the network card. So what you want _is_ possible.

But non-trivial.  IBM also has some code that does a similar thing that
comes with their Token-Ring Network PC Adapter Technical Reference.

|
|-- 
|Leonard Erickson		...!tektronix!reed!percival!bucket!leonard

Jerry Whitnell				Lizzi Borden took an axe
Communication Solutions, Inc.		And plunged it deep into the VAX;
					Don't you envy people who
					Do all the things You want to do?