From: "Tony Ingenoso" 

If there's no "standard" video card, its quite possible. There
were some early DOS machines made that just had serial connected terminal
displays. One sorry outfit in MA I worked for briefly produced a rather
forgettable one everyone working there was forced to use (they couldn't
sell'em to anyone, so the employees had to suffer with them).  Of
course they were grossly incompatable with the IBM PC which might have hurt
sales some

At the low level, the DOS kernel itself doesn't do anything that knows
specifically about video adapters - it just calls the BIOS TTY write
function - so if BIOS shoots it somewhere else like to a terminal out a
comm port or some nonstandard video lashup, DOS is none the wiser.

In reality, a well structured app using overlays, could allow some quite
huge programs to be run in very little memory fairly effectively.  The main
flight computers for the space shuttle worked this way - they are variation
on S/360 architecture (minus some of the business oriented BCD instructions
and byte addressability) and only had 256K. That was enough to run the
whole shuttle for a given flight phase.

The old PL/1 compiler was about 18 or 19 passes and could run on an old
S/360 model 20 with only 64K RAM.  Stallman said nobody would ever
get GCC to run under DOS "it was too big" - until DJ did it
;->  I bet if I wanted to spend a week or two restructuring it a bit
(which I don't), I could make the damn thing fit on a 640K 8088 XT with
some EMS.  DJ copped out and went with the 386 DOS extender
approach

I look back at how well a PDP-11/70 with 128K performed running Unix and
supporting 20 people or so and its disheartening to realize how far our
expectations have been lowered over the years.


"Mike N."  wrote in message
news:fsbb91tqvv7koq9beed1o0bedd1s8afuvj{at}4ax.com...
> On Thu, 26 May 2005 04:15:55 -0400, "Tony Ingenoso"

> wrote:
>
> >Actually, the 640K limit has little to do with the way DOS was designed,
and
> >everything to do with the location of the EGA/VGA graphics memory that
was
> >unfortunately parked at A000:0000.  An unhacked stock DOS with a BIOS
that
> >supports memory scanning beyond 640K (a Taiwan BIOS by an outfit named
RIMOS
> >had one in a clone I had) will happily count memory up to whatever you
have
> >in the box.
>
>   I had a Zenith Z100 MSDOS box and there was some mod you could do to
give
> you 900-someK of RAM (I forget the exact number).   I made use of that to
> run some large programs before LIM/EMS/XMS memory became popular.

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