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From: ballou@chalk.dec.com (Ken Ballou)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Protected mode and PC/XT cards
Message-ID: <1235@hiatus.dec.com>
Date: 7 Jun 89 17:01:22 GMT
References: <30483@conexch.UUCP> <158322@neabbs.UUCP>
Sender: news@hiatus.dec.com
Lines: 22

In article <30483@conexch.UUCP>, rob@conexch.UUCP (Robert Collins) writes:
> So your question really becomes quite simple:  Does video (or any RAM)
> below 1M work on a 286?

I'm sorry, but I'm a bit confused.  (Of course, that is hardly news! :-)
I thought the original question was something along this idea:

Suppose I create a segment whose base address is 180000H.  Now, when I access this segment, address line A20 will carry a 1.  However, as you point out:

>                          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.

Now, specifically since the card only has 20 address lines, won't it ignore A20
being 1?  If so, then it would see 8xxxxH on the low address lines.  Wouldn't it
then say "Aha, you're talking to ME!" and try to respond?  So, as the original
question put it, wouldn't you have video RAM appearing at 080000H, 180000H, 280000H, and so on?

--
Kenneth Ballou		Digital Equipment Corp.
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