Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!amdcad!diablo!phil
From: phil@diablo.amd.com (Phil Ngai)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Protected mode and PC/XT cards
Message-ID: <25894@amdcad.AMD.COM>
Date: 7 Jun 89 21:36:21 GMT
References: <158322@neabbs.UUCP> <30483@conexch.UUCP>
Sender: news@amdcad.AMD.COM
Reply-To: phil@diablo.AMD.COM (Phil Ngai)
Organization: Advanced Micro Devices, Inc. Sunnyvale CA
Lines: 21

In article <30483@conexch.UUCP> rob@conexch.UUCP (Robert Collins) writes:
|In article <158322@neabbs.UUCP> alun@neabbs.UUCP (ALUN SAUNDERS) writes:
|>Can anyone tell me what happens to memory on 8-bit PC/XT add-on cards
|>installed in a 286 or 386 machine, say video RAM, when that machine is
|>running in protected mode ?  Since the card is only seeing the bottom
|>20 bits of the 24 address lines, won't the offending lump of memory
|>appear all over the ........
|
|So your question really becomes quite simple:  Does video (or any RAM)
|below 1M work on a 286?  The answer is an obvious yes.  It doesn't
|matter that you only have 20 address lines on your card when A20-A23
|are 0 anyways.

Try reading the question, fella. Alun wants to know how the card can
tell A20-23 is NOT 0 when it's not connected to A20-23.

Let's hope you're not in charge of developing software or any other
task where you have to understand what an address space is. 
--
Phil Ngai, phil@diablo.amd.com		{uunet,decwrl,ucbvax}!amdcad!phil
"The government is not your mother."