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Corrupted memory managers

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First post, by Nikoh

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On my old PC AT pentium 100 I installed a compact flash card instead of the hard disk.
I use the compact flash card to add files to my dos 7.1 cdu OS; sometimes it happens that the system no longer boots. I have done many tests and I have seen that if I re-copy fresh himem and emm386 onto the compact falsh card, everything starts working again.
This may config.sys:

[menu]
menuitem=A, Extended memory (HIMEM+EMM386 NOEMS)
menuitem=B, Extended + Expanded memory (HIMEM+EMM386)
menuitem=C, Extended memory (JEMMEX NOEMS)
menuitem=D, Extended + Expanded memory (HIMEMX+JEMM386)
menuitem=E, Conventional memory only

menudefault=A,10

[A]
DEVICE=C:\DOS71\HIMEM.SYS /TESTMEM:OFF
DEVICE=C:\DOS71\EMM386.EXE NOEMS I=B000-B7FF

[B]
DEVICE=C:\DOS71\HIMEM.SYS /TESTMEM:OFF
DEVICE=C:\DOS71\EMM386.EXE AUTO RAM I=B000-B7FF

[C]
DEVICE=C:\DOS71\JEMM\JEMMEX.EXE NOEMS X=TEST I=TEST I=B000-B7FF VME

[D]
DEVICE=C:\DOS71\HIMEMX\HIMEMX.EXE
DEVICE=C:\DOS71\JEMM\JEMM386.EXE X=TEST I=TEST I=B000-B7FF VME

[E]

[COMMON]
SET PATH=C:\DOS71;..;
FILESHIGH=40
BUFFERSHIGH=50,0
FCBSHIGH=16,0
LASTDRIVEHIGH=Z
STACKSHIGH=11,512
DOS=HIGH,UMB,NOAUTO
DEVICE=C:\DOS71\ECHO.SYS W/e/l/c/o/m/e /t/o MS-DOS 7.10...
DEVICE=C:\DOS71\ECHO.SYS C/o/p/y/r/i/g/h/t M/i/c/r/o/s/o/f/t C/o/r/p. A/l/l /r/i/g/h/t/s /r/e/s/e/r/v/e/d.
DEVICEHIGH=C:\DOS71\SETVER.EXE
DEVICEHIGH=C:\DOS71\XCDROM\XCDROM.SYS /D:IDE-CD
REM DEVICEHIGH=C:\DOS71\VIDE-CDD.SYS /D:IDE-CD
DEVICEHIGH=C:\DOS71\DISPLAY.SYS CON=(,,1)
NUMLOCK=ON
COUNTRY=039,850,C:\DOS71\COUNTRY.SYS
REM SHELL=COMMAND.COM /P /E:640
SHELL=C:\DOS71\COMMAND.COM /C LH C:\DOS71\COMMAND.COM /E:640 /P
REM DEVICEHIGH=C:\DOS71\SMARTDRV.EXE /DOUBLE_BUFFER
REM DEVICEHIGH=C:\DOS71\IFSHLP.SYS
REM DEVICE=C:\CTCM\CTCM.EXE

and my autoexec.bat:

@ECHO OFF
PATH C:\DOS71\NORTON\NC;C:\DOS71\DOSLFN;C:\DOS71\SHSU3-6;%PATH%
PROMPT $P$G
SET DIRCMD=/A/4/O:GEN
MODE CON RATE=32 DELAY=1
MODE CON CP PREPARE=((850)C:\DOS71\EGA.CPI)
MODE CON CP SELECT=850
LH KEYB IT,,C:\DOS71\KEYBOARD.SYS
LH KILLER
LH DOSKEY
LH SHSUCDX /D:IDE-CD /V /C 
REM LH MSCDEX /D:IDE-CD
LH DOSLFN /Z:C:\DOS71\DOSLFN\CP850UNI.TBL
LH CTMOUSE

SET SOUND=C:\SBLASTER
SET BLASTER=A220 I5 D1 H5 P330 E620 T6
SET MIDI=SYNTH:1 MAP:E MODE:0
SET CTCM=C:\CTCM
C:\CTCM\CTCM
LH C:\SBLASTER\AWEUTIL /S
LH C:\SBLASTER\MIXERSET /P /Q 

ECHO.
REM For locking volumes to enable "direct disk access":
REM CALL LOCKDRV.BAT
BREAK ON
LFNFOR ON
ECHO Now you are in MS-DOS 7.10 prompt. Type 'HELP' for help.
ECHO.

Could it be a virus? I did a scan with microsoft antivirus but it didn't find any viruses.
why do only the memory manager files get corrupted while everything else continues to work?

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Reply 1 of 3, by mkarcher

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Perhaps that flash card has weak sectors? Did you try comparing the corrupted memory managers with the original ones to find out the kind of corruption? Single bit flips are clearly distinguishable from virus infections.

Reply 2 of 3, by Horun

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Good thought mkarcher ! If me would do this next time it happens: rename the files *.bad and leave them and then copy good files onto the CF, that way they would not be using same sectors.
I know that many times deleting a file just removes it from the file table so if you then rewrite the files they end up in same sectors as the supposed deleted ones specially IF no other files were
written to disk after delete and before writing....

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

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