Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!vsi1!octopus!pete
From: pete@octopus.UUCP (Pete Holzmann)
Newsgroups: comp.sys.ibm.pc
Subject: Interesting Info for '386 DOS users
Message-ID: <337@octopus.UUCP>
Date: 26 Aug 88 18:46:47 GMT
Reply-To: pete@octopus.UUCP (Pete Holzmann)
Organization: Octopus Enterprises, Cupertino CA
Lines: 52

I've just finished playing with DesqView and 386-to-the-Max. [DesqView is
a multitasker; 386max emulates EEMS memory, and makes high DOS memory
(above the video area) available for program use, thus freeing up more of
the base 640K for other stuff.]

One of the painful things about a setup like this is that there are various
ROM BIOSes mapped into the high address space. These not only take up
room that I wish was available for programs or Desqview or an EMS page
frame, but they fragment what address space *is* available. For example,
on the machine I'm playing with, the high address space is mapped like this:

	A000-BFFF = EGA Video
	C000-C3FF = ROM
	C800-CBFF or CC00-CFFF = Hard Disk ROM BIOS
	E000-E3FF = ROM BIOS #1
	F000-FFFF = ROM BIOS #2

As you can see, the available address spaces are cut into 3 different small
chunks: 16-32K from C400 to the HD BIOS, 64-80K from there to the first
ROM BIOS, and 48K from there to the second ROM BIOS.

What I have learned is that much of this ROM is not needed most of the time,
and 386max can eliminate it from the address space.

C000-C3FF on my machine is the BIOS for my Vega Deluxe EGA card (I looked
at it with debug). This is needed.

The ROM BIOS at E000 is a spare EGA BIOS that seems to be part of my AMI
BIOS. It is not used, and can be mapped out without a hitch.

I figured the hard disk BIOS was necessary. It isn't, for the most part.
You need it to set up your drives the first time (the 'ol "go into debug
and g=c800:5" trick). It is also used while the machine is booting, to
verify drive parameters. But once the machine is loading config.sys, it
is not used! So 386max can map that out too. I tried this extensively, and
it works. I talked to Adaptec, and they think it should too, although
they want to do more research before they will officially stamp it as an
'approved by Adaptec' technique. Your mileage may vary on other controllers,
but I bet it will work just fine. Don't experiment with other controllers
unless you have a good backup! I'd be interested in hearing reports of
other controllers for which this works or doesn't work.

So, with two ROM's out of the way, I now have contiguous memory available
from C400-EFFF. That's 176K of contiguous RAM! Not bad. I think I *like*
this '386 business!

Pete
-- 
  OOO   __| ___      Peter Holzmann, Octopus Enterprises
 OOOOOOO___/ _______ USPS: 19611 La Mar Court, Cupertino, CA 95014
  OOOOO \___/        UUCP: {hpda,pyramid}!octopus!pete
___| \_____          Phone: 408/996-7746