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Subject: Re: Walking all the physical memory in an x86 system
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Jan Engelhardt <jengelh@linux01.gwdg.de>
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Date: Tue, 30 Nov 2004 20:28:06 +0000
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On Maw, 2004-11-30 at 20:46, Jan Engelhardt wrote:
> I want(ed) to find out which I/O port to use for inb() and stuff, and using the
> BIOS's provided data. If you are referring to "ports", I could not find a
> device node, but "port" maybe:

I didn't know that was in the BIOS page. 

> Oh, look what /dev/mem found! (I retried haha)

> So, /dev/mem points to "physical" mem in a sense like DOS has. (Where, the
> BIOS, is blend into, as you can see)

The kernel also preserves the low 4K because some apps, APM and the like
turned out to need it.