On 4/17/2021 10:23 AM, TK Chia wrote:
Hello Ralf,
The "CALL 5" equivalent was never properly implemented, I guess Peterson
ran into problems with the differences of the 8080 and 8086 CPUs.
[...]
And you will have a hard time to find any serious documentation on that
CALL 5 stuff for any version of DOS. And I would be surprised if there
would have been anything left after the rewrite of DOS for MS-DOS 2.0.
The `call 5' implementation was very clunky --- involving running some
pesky extra instructions not needed by the `int 0x21' path --- but it
most probably did work back then.
In a way, it had to work --- the programs translated using Paterson's
Z80-to-8086 source code translation relied on the `call 5' actually
working as a syscall mechanism.
On a slightly related note: https://www.pcjs.org/blog/2018/05/27/ . :-)
Well, that article has a whole lot of nothing about "CALL 5".
I am working with DOS since December 1981, so that is for almost 39.5
years now, and I have never even once come across a program that would
use it, nor have I ever found any shred of information about using this
"CALL 5" in ANY DOS version. It will not show up in any MS or IBM DOS
(Technical Reference) manual, nor do I recall this mentioned in more
than passing in any 3rd party "DOS internal" kind of books.
The only place where this is ever mentioned, beside in descriptions of
the DOS PSP, stating usually just its mere existence, is in the 86-DOS
Programmer's Manual
(https://web.archive.org/web/20190623112725/http://www.patersontech.com/dos/Docs/86_dos_prog.pdf),
then even there just as a note to it being a tool helping in the
translation of existing CP/M-80 programs, and a clear note that this is
not to be used for any new program (page 7).
By and large, people just need to stop spreading the myth that "DOS is
copied/stolen from CP/M" or similar nonsense.
Ralf
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