AW: CGA card (Mitsubishi Electric) with 192K RAM?

[Fred Cisin]

>> "DOS based utility program to poke at the contents and/or snarf the int a 
>> file on disk"?
>> DEBUG.COM
>
On Mon, 7 Sep 2020, Jules Richardson via cctalk wrote:
> Funny, I've only ever used it for quick bits of assembly (just a couple of 
> days ago, in fact), and to do things such as kicking off the formatter 
> embedded in the ROM on some controllers. It didn't even occur to me that it 
> probably has some dumping/loading abilities too! I'll dig some docs out...

1) If the drive is larger than 32MB, then boot with DOs 3.31 or newer.
Although even with the older ones, you can still do quite a bit.  3.31 is 
the first where DOS supports a partition larger than 32MB
MS-DOS 5.00 is first where debug commands have a "/?" option to get a 
short reminder of usage.

If running DEBUG gives you an "INCORRECT DOS VERSION" error, then find the 
right one, OR (DOS 5.00 or above), figure out what DOS version that copy 
of DEBUG is demanding, and use SETVER.


L 100 2 0 1
will load into DS:100, the contents of drive 2 (C:), first sector, 1 
sector   (which happens to be the Master Boot Record and Partition Table)

D                  ; will display it.
D [address]        ; will let you look at other areas in the segment.

R                  ; see register contents

N [filename]       ; select filename
R CX
200                ; set CX to 512;  make sure BX is 0
W                  ; write BX:CX bytes from DS:100 to the file

To write 8K from c800:0 to file "TMPCX.DAT":
R DS
C7EO               ; compensate for offset 100
R CX
2000               ;8K
N A:TMPCX.DAT
W

The offset :100 is a carryover from the PSP and TPA of CP/M.


Q                  ; the absolutely most important DEBUG command to know

Finding the errors in the above from my aging unrefreshed dynamic wetware
is left as an exercise for the reader.


There are MANY people on this list that have plentiful experience and 
better memories.