OT: Re: Security question (sort of)/goodbye - test-drb@ccmp.vtda.org

21 Mar 1999

What the BIOS does, in this case, isn't relevant, though that should work, I
guess.  It's what M$ did in MSD and Windows that matters, since that's
what's getting confused.

Dick

-----Original Message-----
From: Tony Duell &lt;ard(a)p850ug1.demon.co.uk&gt;
To: Discussion re-collecting of classic computers
&lt;classiccmp(a)u.washington.edu&gt;
Date: Sunday, March 21, 1999 12:53 PM
Subject: Re: OT: Re: Security question (sort of)/goodbye

...
   As for the
serial ports, the UART or maybe ART (also a valid acronymn, I 
You know, I've heard of (and used) UARTs, USRTs, USARTs, ACIAs, ACEs
(Async Communcation Element, I think, which it what Intel called the
8250). Never ARTs...

  guess, since they're hardly universal any
more) these are normally
 recognized by means of the interrupt they return.  If, let's assume, the 
Well, the PC/AT simply looks at the Interrupt ID registers of the UARTs at
$3FA and $2FA. If it gets the right value back, it assumes the UART
exists. I've just checked the BIOS source listing (section TEST2)

Of course modern BIOSs probably do something totally different, but without
the source listing it's impossible to be sure.

-tony