Path: utzoo!utgpu!attcan!uunet!tektronix!tekcrl!tekgvs!toma
From: toma@tekgvs.GVS.TEK.COM (Tom Almy)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 640kb limit on DOS?
Keywords: PS-2/50 DOS
Message-ID: <4375@tekgvs.GVS.TEK.COM>
Date: 14 Dec 88 15:30:28 GMT
References: <8043@ihlpl.ATT.COM> <3521@nicmad.UUCP> <593@tapa.UUCP> <10687@s.ms.uky.edu> <3534@nicmad.UUCP>
Reply-To: toma@tekgvs.GVS.TEK.COM (Tom Almy)
Distribution: na
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 52

In article <3534@nicmad.UUCP> brown@nicmad.UUCP (Vidiot (Vid-e-it)) writes:
<In article <10687@s.ms.uky.edu> simon@ms.uky.edu (Simon Gales) writes:
<<In article <593@tapa.UUCP> larry@tapa.UUCP (Larry Pajakowski) writes:
<<<You can cheat on the 640k barrier with a 386 or an All Charge Card.
<<< ...
<<
<<With a 386 box, running DOS 3.x, how does one cheat on the 640k limit?
<<Yes the box has bios shadow ram and exteded memory, but how exactly can
<<a 386 help you break DOS's 640k limit?
<
<PS/MS-DOS does not, nor can it ever, access anything except the first 1 MB
<of memory.

Buy a copy of Phar Lap DOS/EXTENDER, and compilers from either Metaware or
Microway.  This will cost at least $1,000, but then you can write programs
that run in the 80386 Protected mode.  The advantages are:

1.	Extended memory and the lower 640k are mapped (using the built in
	paging registers) into one contiguous memory.

2	All programs are "small model", small being 4 gigabytes, so run
	faster than their 8088 compiled large model equivalents.

3	You can take advantage of the 32 bit data paths, registers, and
	arithmetic.  Slopily written VAX UNIX programs stand a better 
	chance of running because sizeof(int) == sizeof (*in) == sizeof (long.

4	Demand paged virtual memory is almost available (at extra cost).

5	Almost all DOS calls (main exception being the older CP/M style
	file functions) are handled by the PharLap package, which passes them
	back to MS DOS for handling.  You don't see any performance hit, even
	with highly I/O intensive code.  You can also write interrupt routines
	which run in either real or protected mode.

The PharLap package includes a Microsoft style assembler.  Metaware has
advanced C and Pascal compilers.  Microway has C, Fortran, and Pascal 
compilers that are more in the UNIX fashion (C isn't ANSI, they produce
asm code which gets assembled, command options like UNIX...).

Using this environment I have successfully compiled xlisp, microemacs, and
Spice 2G.6.

Also for the 80386 is Laboratory Microsystems UR/FORTH 386, which at $350
gives a cheaper way to play around in protected mode (Phar Lap product not
needed).  It includes an assembler and Forth machine code compiler besides
the normal interpreted environment.

 Tom Almy
toma@tekgv.tek.com
Standard Disclaimers Apply, except I wrote the 80386 Forth compiler for
which I receive a royalty worth about a dinner at McDonalds.