Category : Alternate Operating Systems - Quarterdeck DesqView, CP/M, etc
Archive   : DRTIPS.ZIP
Filename : 1116.TXT

Document 1117
SID memory detection of ROMs
04/13/92
BK

SID, THE MEMORY DETECTOR


Occasionally when loading DR DOS 6.0's EMM386.SYS memory
management driver, one will find that the MEM /A display shows an
area of upper memory excluded from use. After attempts to access
the memory area through the use of the /Include or /Use switches
for EMM386.SYS have failed, one might begin to suspect that some
memory addressed ROM chips are occupying that area. One can use
DR DOS 6.0's SID to check on that. To do this, load SID and have
it search the desired areas of memory for a copyright. If one is
found, displaying it will probably tell one which piece of hard-
ware is using the memory addresses. Below is an example:

Here is an excerpt of a MEM /A display that shows an area exclud-
ed at D7FF:0000 and a ROM chip at D800:0000 (the exclusion will
precede the ROM chip itself to protect the ROM's address).

³ CF00:0000 ³ -------- ³ 9000h, 36,864 ³ ---------- Upper RAM
ÃÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
³ CF00:0000 ³ DR DOS ³ 8FF0h, 36,848 ³ System
³ CFE3:15C0 ³ DR DOS ³ DE0h, 3,552 ³ DR DOS BIOS code
³ D7FF:0000 ³ EXCLUDED ³ 2010h, 8,208 ³ Upper system memory
ÃÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
³ D800:0000 ³ -------- ³ 2000h, 8,192 ³ ------------- ROM ---
³ DA00:0000 ³ -------- ³ 16000h, 90,112 ³ ---------- Upper RAM
ÃÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
³ DA00:0000 ³ DR DOS ³ 9450h, 37,968 ³ System
³ D701:3000 ³ DR DOS ³ 9440h, 37,952 ³ DR DOS kernel code

To get SID to investigate that area, first load SID. SID will
display its '#' prompt. Tell it to search the area of memory
using the SR command looking for all the permutations of copy-
right markings. For example, the MEM display shows something at
D800:0000, so use the command

SRD800:0000,FFFF,"COPYRIGHT
|_______|-> Change this number to investigate different
areas of memory.

"COPYRIGHT","Copyright","copyright","(C)",and "(c)" will usually
cover all the bases. Notice that upper case/lower case IS impor-
tant. If SID finds some data in memory that matches one's search
parameters, it will display the address of that data in the
SEGMENT:OFFSET format. There may be more than one. Record those
addresses. Then display the data at each of those locations using
the D command. The company name should give one some idea of the
hardware occupying the area of memory. Below is what the investi-
gation of the above machine looks like:
[DR DOS] C:\>SID
--------------------------------------------------
*** Symbolic Instruction Debugger *** Release 3.2
Copyright (c) 1983,1984,1985,1988,1990,1991
Digital Research, Inc. All Rights Reserved
--------------------------------------------------
( COMMENTS )
#SRD800:0,FFFF,"COPYRIGHT ( Nothing found )

#SRD800:0,FFFF,"copyright ( Nothing found )
#SRD800:0,FFFF,"Copyright
D800:0056 ( BINGO !! )
#DD800:0056 ( Display that area )

D800:0056 43 67 68 74 20 28 43 29 20 31 39 Copyright (C) 19
D800:0066 38 42 54 72 61 6E 74 6F 72 20 53 89-90, Trantor S
D800:0076 79 73 2C 20 4C 74 64 2E 0D 0A 00 1A ystems, Ltd.....
D800:0086 00 07 73 01 CB 8D 36 34 00 E8 A6 04 ....9.s...64....
D800:0096 B8 C6 06 74 00 00 C6 06 75 00 00 C6 [email protected]...
#

The copyright is held by the company that made the card that
connects to the CDROM player in this particular machine, thus the
presence of the card is why this area of memory is excluded.