Path: utzoo!attcan!uunet!husc6!cmcl2!nrl-cmf!ames!ucsd!ucsdhub!hp-sdd!hplabs!hpda!hpcupt1!hpcuhb!hpindda!vandys
From: vandys@hpindda.HP.COM (Andy Valencia)
Newsgroups: comp.arch
Subject: Re: Re: negative addresses (really unsigned arithmetic)
Message-ID: <3450004@hpindda.HP.COM>
Date: 15 May 88 15:57:50 GMT
References: <11571@ut-sally.UUCP>
Organization: HP Technical Networks, Cupertino, Calif.
Lines: 11


	Logitech got caught by the "NIL doesn't have to be 0" syndrome.
I think they used 0xFFFF,0xFFFF.  Turns out that the 80286
architecture traps loads of invalid segment numbers into the
segment registers, but allows 0 to be loaded, and then traps the
reference instead.  So unless you're representing at least the segment
number as 0, you're not going to survive protected mode '286.
In their new compiler I believe NIL is now 0,0xFFFF.

				Andy Valencia
				vandys%hpindda.UUCP@hplabs.hp.com