From: "H. Peter Anvin" <hpa@zytor.com>
To: Rene Herman <rene.herman@gmail.com>
Cc: Bart Trojanowski <bart@jukie.net>, linux-kernel@vger.kernel.org
Subject: Re: how to tell linux (on x86) to ignore 1M or memory
Date: Thu, 21 Jun 2007 18:46:02 -0700 [thread overview]
Message-ID: <467B29DA.9040309@zytor.com> (raw)
In-Reply-To: <46290DED.80500@gmail.com>
Rene Herman wrote:
> On 04/19/2007 04:18 PM, Bart Trojanowski wrote:
>
>> I need to preserve some state from the bios before entering protected
>> mode. For now I want to copy it into some ram accessible by
>> real-mode, say the last megabyte visible in real-mode.
>>
>> What's the easiest way to have linux ignore the megabyte starting at 15M?
>
> Note that real-mode can only access the first megabyte (*) and not the
> first 16. 16MB is the 16-bit protected mode (286) limit.
>
No, 16-bit protected mode (on 386+) is not limited to 16 MB.
The main reason there is a 16 MB limit in some current systems is that
ISA, and the ISA DMA controller only had 24 address lines.
-hpa
next prev parent reply other threads:[~2007-06-22 1:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-19 14:18 how to tell linux (on x86) to ignore 1M or memory Bart Trojanowski
2007-04-19 14:30 ` Paolo Ornati
2007-04-20 19:01 ` Rene Herman
2007-06-22 1:46 ` H. Peter Anvin [this message]
2007-06-22 13:16 ` Rene Herman
[not found] <8bFEz-3B4-39@gated-at.bofh.it>
[not found] ` <8c6EE-4Jj-5@gated-at.bofh.it>
2007-04-20 21:39 ` Bodo Eggert
[not found] ` <8yGrK-4vX-7@gated-at.bofh.it>
[not found] ` <8yRnb-4XE-23@gated-at.bofh.it>
2007-06-22 23:00 ` Bodo Eggert
2007-06-22 23:04 ` Rene Herman
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