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Date: Mon, 6 Feb 1995 17:32:07 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199502060632.RAA32253@godzilla.zeta.org.au>
To: kuku@gilberto.physik.rwth-aachen.de, terry@cs.weber.edu
Subject: Re: Bios basemem (637K) != RTC basemem (640K)
Cc: freebsd-hackers@freefall.cdrom.com
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>Subject: Re: Bios basemem (637K) != RTC basemem (640K)
>> 
>> Excuse my ignorance, but what does that mean? Do I have to worry?

It means that your BIOS reserves 3K of memory for internal use and
O/S's that use the BIOS see only 637K of base memory instead of 640K.
FreeBSD currently sees both and uses 640K.  This may change.  The
handling of extended memory _will_ change to support systems with
more than 64MB.  FreeBSD should never have looked in the CMOS for
the memory sizes.

>It means that either your BIOS starts counting at 0 and something swiped
>2k of memory, or your BIOS starts counting a 1 and someone swiped 3k of
>memory.  Or your BIOS starts counting at -2 and nothing is swiping any
>memory at all.

This confusion may apply to the memory size in the CMOS (I don't think
it does; I think some BIOS's just pre-allocate the memory that they are
going to steal from the top of base memory) but it doesn't apply to
the BIOS memory-size call.

>Depending on your machine and BIOS, it's probably nothing worse than
>the user configurable IDE drive table.

This is a standard feature of AMI BIOS's.  Don't use it unless you have
to.

Bruce