🚀 go-pugleaf

In article <394@catnip.UUCP>, ben@catnip.UUCP (Bennett Broder) writes:
> In article <985@husc2.UUCP> shields@husc2.UUCP (shields) writes:
> >I am an experienced user of PC-DOS, but I am still unclear on
> >the exact differences between MS-DOS and PC-DOS.
>
> There is little if any difference between MS-DOS and PC-DOS.  They are
> both the same OS, but PC-DOS is supported by IBM instead of Microsoft
> or another hardware vendor.
> 
> I have only found one real difference:
> 
> * PC-DOS comes with BASIC and BASICA, which utilize the cassette
>   basic ROMS on real IBM PCs and ATs.  MS-DOS comes with GWBASIC,
>   which is self-contained.  BASICA leaves a trife more, and BASIC
>   leaves substantially more free memory for your BASIC code and variables
>   than GWBASIC.
> 
> Of course, IBM and other OEMs may make certain changes that will prevent
> their version of MS-DOS from working on another vendor's computer, however
> there should not be any difference in functionality between these different
> versions.


Sorry, but I couldn't disagree more!

MS-DOS is a generic product which is sold to OEM's.  It provides all of
the system functions and calls that are accessed via interrupts above 20h
(i.e., int 20h, int21h, etc.)  This generic, base system is sometimes
slightly customized by the OEM (IBM does this to a minor degree, I'm told).
The basic operation of MS-DOS, and the functions provided via these rupts
are very well defined and consistent from vendor to vendor.  But that's
where it stops.

All of the functions/services that are provided by the BIOS are up to
the individual vendor to implement, and are implementation specific.  On
PClones these are things like rupts 10h - 1Fh, which provide services
for Video I/O, RS232, keyboard, printer, Basic, floppys, etc. (at the
BIOS level).  Then there are what are usually called H/W rupts (08h - 0Fh)
on PClones;  these too, are implementation specific.

There are several machines that run MS-DOS, but are in no way compatible
with IBM PC's or PClones, and have vastly different H/W and BIOS functions.
For example, my Fujitsu Micro-16s runs MS-DOS (2.11, currently), but
very little PC software (unless the s/w has been written to be MS-DOS
compatible, or a port has been done specifically for the Fuji machine).

To illustrate, the Fuji machine does not have memory-mapped video I/O,
but rather has a seperate I/O Subsystem and Processor (a 6809) that takes
care of this (and other types of I/O).  It uses a small, dual-ported RAM
that lives in the I/O instruction space of the 8086 processor to pass
data back and forth to the 6809, which really does the actual I/O oper-
ations.  (That's right, from the 8086's point of view, I/O is performed
using real IN and OUT instructions, plus a well-defined handshaking
protocol).  This is in NO WAY even close to the way PClones do Video I/O;
other BIOS-level functions are just as different.  Needless to say, all
the BIOS interfaces were written by Fujitsu, even though they interface
to Microsoft's MS-DOS.

The term PC-DOS is usually used to refer to the collection of MS-DOS
*and* the BIOS and H/W rupt support as implemented by IBM PC's (and "true
compatibles").  The BIOS part may be realized in s/w on a floppy, or may
be in ROM, or a combination of the two.

There are other pieces of the puzzle as well.  Things like the ANSI.SYS
and CONFIG.SYS files, etc.  Generally, these can be considered to be part
of the BIOS, and are (usually) implementation specific.  (You should see
what my Fuji does ... or tries to do ... when I try to use NANSI.SYS or
FANSI.SYS in place of the ANSI.SYS that Fuji supplies :-)!)

I short, while the MS-DOS part of the system s/w may be portable from
one vendor's machine to another, the BIOS/etc. parts may or may not be,
and then only if the machines are PClones.

What I really find annoying are advertisements that say something like:
"requires an IBM PC/XT/AT, and MS-DOS 2.xx or 3.xx".  This is a totally
meaningless statement, which may mean that what's required is a PClone
running PC-DOS, or it may mean it'll work on any 8086/8088/80186/80286
machine running MS-DOS, or ...

/kim


P.S.  I recently installed a board in the Fuji that provides about a 95%
      level of PC compatibility.  If anyone is interested in the details,
      send me email.


-- 
UUCP:  {sun,decwrl,hplabs,pyramid,ihnp4,seismo,oliveb}!amdahl!kim
DDD:   408-746-8462
USPS:  Amdahl Corp.  M/S 249,  1250 E. Arques Av,  Sunnyvale, CA 94086
CIS:   76535,25

[  Any thoughts or opinions which may or may not have been expressed  ]
[  herein are my own.  They are not necessarily those of my employer. ]