Weird. Does MSD give any clues about what might be taking the 6K? Is there onboard video or onboard anything else?

Clean MS-DOS install on fresh spare hdd is what I would try next. Right after the clean install, does it show 634?

Have you gone through the BIOS and set it to fail safe defaults? That might turn something off that gives you a clue.

del

clueless1 wrote:

Weird. Does MSD give any clues about what might be taking the 6K? Is there onboard video or onboard anything else?

No. The board is Chaintech 4SLD.3, no onboard video, no onboard HDD/FDD ctrlr.
About MSD, where exactly can I browse the memory in this program? I've never used it deeply before. Sorry for stupid question.

clueless1 wrote:

Clean MS-DOS install on fresh spare hdd is what I would try next. Right after the clean install, does it show 634?

I've reinstalled the MS-DOS on multiple HDDs for >10 times!
Yes, RIGHT after a clean install I get 634 conventional mem, and all these problems with emm386, bc++, etc.

clueless1 wrote:

Have you gone through the BIOS and set it to fail safe defaults? That might turn something off that gives you a clue.

Well, my BIOS does not have any "fail safe defaults", 🤣.

---

Look, looks like all of these problems I described above appear ONLY if I am using ~ >170Mb HDD. How is it possible?
When I use <=170Mb HDD, everything works _as_it_should_. (and I've tried with different IDE controllers, no difference at all).

Isn't that missing memory probably the extended bios data area? I've never seen a system take 6k for EBDA but 1/2/4k is pretty common.

keenerb wrote:

Isn't that missing memory probably the extended bios data area? I've never seen a system take 6k for EBDA but 1/2/4k is pretty common.

I don't think my motherboard's BIOS even have any extended data area.

I'm not sure, but can't some cards with seperate ROMs allocate EBDA as well?

keenerb wrote:

I'm not sure, but can't some cards with seperate ROMs allocate EBDA as well?

I dunno. I've erased sound card (SB16), HDD, CD-ROM drive, booted from floppy (MS-DOS 6.22 installation floppy 1), mem still says I've got 634K of conventional memory.
Now it says the same even when I boot from 170Mb HDD, but it didn't do that an hour ago and everything was OK! I'm completely lost.

xstraski wrote:

mem shows 634K total conv.
mem/c/p shows 649,216 total conv.

634*1024=649216, to be sure.

I am not sure what the concern is here. COMMAND.COM would be expected to take up 6K.

Jorpho wrote:

xstraski wrote:

mem shows 634K total conv.
mem/c/p shows 649,216 total conv.

634*1024=649216, to be sure.

I am not sure what the concern is here. COMMAND.COM would be expected to take up 6K.

And why then MEM says the TOTAL (not free) conventional memory is < 640?

Oh. Apologies, I lost the thread of the conversation.

I don't suppose it's worth double-checking whether your MS-DOS installation floppy is infected?

Jorpho wrote:

Oh. Apologies, I lost the thread of the conversation.

I don't suppose it's worth double-checking whether your MS-DOS installation floppy is infected?

F-PROT?

Just to be clear, you're having the same problems across multiple motherboards, multiple CPUs, and multiple sets of memory?

What expansion cards are installed?

Try downloading and installing Opendos or Freedos.

keenerb wrote:

Just to be clear, you're having the same problems across multiple motherboards, multiple CPUs, and multiple sets of memory?

What expansion cards are installed?

Try downloading and installing Opendos or Freedos.

Yes.
Installed Sound Blaster Vibra 16, GoldStar IDE controller, Cirrus Logic VLB video card.

What about RAM? Are you using the same RAM across all motherboards? I don't personally think the 634k of ram is a major concern; even if it's a virus it shouldn't cause weird problems like this.

I'd try to swap out the components you're using one at a time. Remove the SB, use an on-board controller if any of your systems have them, try OpenDos from a FRESH set of diskettes. Even if you use ISA instead of VLB controllers/video card it may help identify any problematic hardware.

keenerb wrote:

What about RAM? Are you using the same RAM across all motherboards? I don't personally think the 634k of ram is a major concern; even if it's a virus it shouldn't cause weird problems like this.

I'd try to swap out the components you're using one at a time. Remove the SB, use an on-board controller if any of your systems have them, try OpenDos from a FRESH set of diskettes. Even if you use ISA instead of VLB controllers/video card it may help identify any problematic hardware.

I've tried various RAM cards, various capacities, 4, 8, 16 Mb.
On Abit AB-SM5 Pentium motherboard everything got OK when I used DIMM 32Mb, but not SIMM 16Mb.
On Amptron PM-8900 Pentium motherboard I still got all these errors even when I used DIMM 32Mb.

And it can't be virus. I've formatted the hard drive. I've reformatted the MS-DOS installation floppies. I also tried to install from CD-ROM in a different computer (Pentium 3).
I've erased SB. I've tried ISA video card, instead of ISA/VLB. I've tried different IDE controllers. NO RESULT. Still the same problems with some games, Borland C++, 634k, and smartdrv<->EMM386.
And my 486 motherboards have no on-board controller.

keenerb wrote:

I don't personally think the 634k of ram is a major concern

Maybe, but I don't have any of those problems I described above if MEM shows 640, but not 634.

This is nightmare.

Have you tried a fresh autoexec/config? Maybe take Phil's template which makes it easy to try EMS, XMS and conventional only:
http://www.philscomputerlab.com/ms-dos-starter-pack.html

One other thing you can try (if you haven't already). You say your Pentium system doesn't have this issue, but your 486 system does. Try swapping hard drives between the two rigs and see if the problem follows the hard drives or stays with the system.

Some rootkits can survive a format. Try a rootkit scan. This one will have to be run from Windows XP or higher:
http://www.bleepingcomputer.com/download/tdsskiller/
Connect your DOS drive as D: (or whatever) and run tdsskiller. It will do the majority of it's scanning on your Windows drive, but it will check the MBR of the other physical drives (check the Report after the scan completes). There may be better rootkit scanners for running in DOS, check here: http://www.hiren.info/pages/bootcd

FYI, on my Pentium system, if I run EMM386, my total conventional is 640. If I run XMS or conventional only, it says 639K. On my 486, it says 640 no matter what memory manager I use. Not sure how useful that is, but it's interesting and I never noticed it til now.

And sorry if I'm giving info you've already tried, I know how frustrating this is, but I'm just throwing info out hoping something is helpful.

Good luck!

If you're familiar with linux you can use 'dd' to do a full wipe of the entire disk, rather than relying on whatever the 'format' command does or doesn't do. Then you'll know for sure that everything on the disk is wiped out of existence.
Another tool that should have the same effect is DBAN (Darin's Boot and Nuke, or whatever his name is). No need to waste time with any of the paranoid multi-pass random number nonsense, just a (relatively quick) zero fill of the whole disk surface is all you're after.

Have you tried resetting the CMOS? After doing that, load conservative defaults (whatever your BIOS calls it, if such an option exists).
There can be things corrupted in the CMOS that do not show up in the setup screen. A full reset and loading defaults is the only way to definitely reset everything in such a situation.

clueless1 wrote:

Have you tried a fresh autoexec/config? Maybe take Phil's template which makes it easy to try EMS, XMS and conventional only: h […]
Show full quote

Have you tried a fresh autoexec/config? Maybe take Phil's template which makes it easy to try EMS, XMS and conventional only:
http://www.philscomputerlab.com/ms-dos-starter-pack.html

One other thing you can try (if you haven't already). You say your Pentium system doesn't have this issue, but your 486 system does. Try swapping hard drives between the two rigs and see if the problem follows the hard drives or stays with the system.

Some rootkits can survive a format. Try a rootkit scan. This one will have to be run from Windows XP or higher:
http://www.bleepingcomputer.com/download/tdsskiller/
Connect your DOS drive as D: (or whatever) and run tdsskiller. It will do the majority of it's scanning on your Windows drive, but it will check the MBR of the other physical drives (check the Report after the scan completes). There may be better rootkit scanners for running in DOS, check here: http://www.hiren.info/pages/bootcd

FYI, on my Pentium system, if I run EMM386, my total conventional is 640. If I run XMS or conventional only, it says 639K. On my 486, it says 640 no matter what memory manager I use. Not sure how useful that is, but it's interesting and I never noticed it til now.

And sorry if I'm giving info you've already tried, I know how frustrating this is, but I'm just throwing info out hoping something is helpful.

Good luck!

I said that I have this problem with 486\pentium motherboards of 94-96.
Actually, I've installed DOS on Pentium III machine to test. And you know what? I get 634K of conv.mem, smartdrv<->emm386 incompatibility even there!

OK, I ll try a rootkit scan.

shamino wrote:

If you're familiar with linux you can use 'dd' to do a full wipe of the entire disk, rather than relying on whatever the 'format […]
Show full quote

If you're familiar with linux you can use 'dd' to do a full wipe of the entire disk, rather than relying on whatever the 'format' command does or doesn't do. Then you'll know for sure that everything on the disk is wiped out of existence.
Another tool that should have the same effect is DBAN (Darin's Boot and Nuke, or whatever his name is). No need to waste time with any of the paranoid multi-pass random number nonsense, just a (relatively quick) zero fill of the whole disk surface is all you're after.

Have you tried resetting the CMOS? After doing that, load conservative defaults (whatever your BIOS calls it, if such an option exists).
There can be things corrupted in the CMOS that do not show up in the setup screen. A full reset and loading defaults is the only way to definitely reset everything in such a situation.

Yes, I am familiar with linux, may be I'll use dd if a rootkit scan won't help.

Yes, I tried reseting the CMOS. Multiple times. Didn't help.

I like shamino's suggestions. DBAN (or dd) one of your drives and install from scratch. If that fixes it, you'll want to DBAN any other drive you're suspicious of. And I would be very careful about the source of your MS-DOS installation media. If somehow it's on there, then you're right back to square one when you reinstall.

I meant to swap drives from your 97-98 Pentiums. So take a drive from your 486 and put it into a 97-98 Pentium PC. Boot up and check if the problem is there.