Message-ID: <01FD6EC775C6D4119CDF0090273F74A4021FA5@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? - Correction
Date: Wed, 28 Feb 2001 10:14:59 +1100
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Reply-To: opendos AT delorie DOT com

It's clearly been too many years and my memory bits are fading!  :-/

Obviously, I wouldn't be using EMM386 on an XT, so I guess
it must be the kernel that checked for (and found!!!) extended
memory on an old XT!

Another interesting bug was that, even when told NOT to use
extended memory, the Task Switcher would still "play around"
with the non-existent extended memory and "hang" the machine!

Anyway, enough about XT's ...   ;-)

Joe.

> -----Original Message-----
> From:	da Silva, Joe 
> Sent:	Wednesday, 28 February 2001 9:45
> To:	'opendos AT delorie DOT com'
> Subject:	RE: Total memory?
> 
> 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