From: Damian Yerrick <DONT DOT YOU DOT DAREd_yerrick AT hotmail DOT comSEND DOT SPAM>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Fastest bitblt?
Organization: Pin Eight Software  http://pineight.8m.com/
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NNTP-Posting-Date: Mon, 28 Feb 2000 15:26:44 GMT
Distribution: world
Date: Mon, 28 Feb 2000 15:26:44 GMT
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

On Mon, 28 Feb 2000 12:05:57 +0200, Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
wrote:

>On Mon, 28 Feb 2000, Damian Yerrick wrote:
>
>> Protected mode only provides a mechanism for memory protection; it
>> doesn't require that operating systems provide such protection.
>
>Not true.  Memory protection is built into protected mode,
>at least to some degree.

But an OS can entirely disable it (e.g. what Watcom DOS4GW or
DJGPP nearptr do).

>Access rights checking and segment-level protection are 
>always active, as they are inherent to PM.

That is, unless the OS gives user programs access rights to all
memory in one fell swoop, allowing them to overwrite the kernel.

>Page-level protection is optional.

And is how Windows 9x and NT do it IIRC.

-- 
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