Message-ID: <01FD6EC775C6D4119CDF0090273F74A4021FA4@emwatent02.meters.com.au>
From: "da Silva, Joe" <Joe DOT daSilva AT emailmetering DOT com>
To: "'opendos AT delorie DOT com'" <opendos AT delorie DOT com>
Subject: RE: Total memory?
Date: Wed, 28 Feb 2001 09:44:47 +1100
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Reply-To: opendos AT delorie DOT com

I don't have the luxury of so much memory to "play with", so
I can't verify this stuff ...   ;-)

However, this is a BIOS interrupt, so it should report how much
actual extended memory exists, not how much any XMS driver
is able to deliver (that's what the original query wanted to find
out - how much actual memory existed).

Also, AFAIK, this interrupt is safe to use on an XT/286, so a
check for 286+ CPU will tell you if it's safe. On this same
topic, and related to (the otherwise-very-very-stable) DR-DOS
6.0, the kernel or EMM386 used this interrupt (IIRC) for this
purpose, without checking the machine type first! On my old
XT, this didn't actually crash the machine, but it did return
garbage which DR-DOS 6.0 interpreted as the amount of
extended memory available. Don't know if this bug was fixed
in latter versions of DR-DOS, but it's something to be aware
of, if you happen to collect PC "museum pieces".

Joe.

> -----Original Message-----
> From:	Bernie [SMTP:bernie AT mbox302 DOT swipnet DOT se]
> Sent:	Wednesday, 28 February 2001 4:39
> To:	opendos AT delorie DOT com
> Subject:	RE: Total memory?
> 
> Joe wrote:
> >The amount of extended memory is returned by interrupt $15, function
> >$88. Beware however, that interrupt $15 can crash some XT machines!
> 
> But isn't this limited to the ammount the XMS driver can handle?
> I don't know the limit for DR-DOS but MS-DOS 6.x has the limit at 64MB. If
> you copy himem.sys from 7.x you get a lot more - I haven't tried to figure
> out the limit since 128MB "should be enough for everyone" ;-)
> //Bernie