FYI, https://theretroweb.com/motherboards/s/auva-c … mputer-npm16-a0

or one of the others that looks so awfully similar.

though the numbers underneath the stickers do seem to match.

weedeewee wrote on 2024-03-07, 16:25:

FYI, https://theretroweb.com/motherboards/s/auva-c … mputer-npm16-a0

or one of the others that looks so awfully similar.

though the numbers underneath the stickers do seem to match.

Yup, I was just looking at that entry. Seems like the nearest match so far. Especially like picture 4 of 14 on that page.

The difference seems to be that I lack a JP7 jumper - but then again, so do many of the motherboards on the pictures on that link (and, just like the mobos displayed on the images, mine is obviously not 22x22 cm).

Fiddling around with the motherboard and removing it from the case, I did manage to pierce the skin of my left index finger, resulting in some blood on the PCB and some traces:

Using a Q-tip, I did manage to get it all off (at least from what I can see):

Am I good or should I be worried about this?

Some pictures of the motherboard:

Okay, I re-installed the motherboard into the case and booted it up. HIMEM.SYS now works? I don't know what I did or how I did it, but it works.

Thanks to all of you who followed me along on this strange journey.

boggit wrote on 2024-03-07, 17:42:

Okay, I re-installed the motherboard into the case and booted it up. HIMEM.SYS now works? I don't know what I did or how I did it, but it works.

Thanks to all of you who followed me along on this strange journey.

The gods accepted your blood offering.

(just kidding)

weedeewee wrote on 2024-03-07, 18:20:

The gods accepted your blood offering.

Yes.

weedeewee wrote on 2024-03-07, 18:20:

(just kidding)

I'm not.

boggit wrote on 2024-03-07, 14:06:

UPDATE: Okay, this is quite a head-scratcher. I switched out the two 4MB SIMM cards, replacing them with two 1MB SIMMs from my 286 mobo (as one can not, according the jumper manuals of all the likely motherboard suspects listed by BitWrangler [here], run 4MB using just one 4MB SIMM card).

Same A20 error as before and - here is the kicker - with /M:1, DOS reports the same unreliability error on the exact same address (00100000h).

The address you quote is the start of the XMS - so this is just another symptom of a non-functional A20 address line. As you get the same error with two different sets of memory modules, faulty memory is very unlikely to be the cause.

boggit wrote on 2024-03-07, 17:42:

Okay, I re-installed the motherboard into the case and booted it up. HIMEM.SYS now works? I don't know what I did or how I did it, but it works.

I guess there was an actual short between the A20 gate control line and ground, making the A20 gate permanently closed. Cleaning the board, or inserting it in a slightly different position, preventing a possible short at an installation bolt probably cleared that short, so A20 control now works fine.

boggit wrote on 2024-03-07, 18:27:

Yes. […]
Show full quote

weedeewee wrote on 2024-03-07, 18:20:

The gods accepted your blood offering.

Yes.

weedeewee wrote on 2024-03-07, 18:20:

(just kidding)

I'm not.

that pleases them.

anyway. enjoy !
and if it somehow re-occurs, it's likely a bad contact. Somewhere on the board. or that what mkarcher stated.

Glad it's working now, yeah defoprobablymaybe a short or something cleared, or just mild flexion of the KBC socket rubbed off some oxide and let metal touch, or the blood sacrifice did it.

The "take it all apart and put it back together again" thing is almost as good as "turn it off and on again" sometimes.

The blood sacrifice is real.

I did clean off some smudge on the back of the PCB (that I don't think was from me bleeding on it), close to where keyboard controller and the SIMM cards are:

boggit wrote on 2024-03-07, 16:48:

Fiddling around with the motherboard and removing it from the case, I did manage to pierce the skin of my left index finger, resulting in some blood on the PCB and some traces:
...
Am I good or should I be worried about this?

The joke between me & my friends back in the days when there was only sharp edged cases and through hole components was that the computer was not going to work until it received a blood sacrifice.

kingcake wrote on 2024-03-06, 20:19:

Gate A20 is controlled by the keyboard controller, right? I would check that over the ram.

Hello,

Just to note that the A20 port isn't always controlled by the keyboard chip.

Even if pin 21 of the Intel 8042 opens correctly for the init, it may not be wired in the motherboard at all.
Indeed, some highly integrated chipsets, like the ALi M1217, embed a lot of internal logic, including the A20.
And if the init synchronization is not good (electronic power supply issue, problem inside the chipset, etc.), the A20 might not work.

Worse yet, sometimes the BIOS is just buggy.
For example bellow, if you load this option, HIMEM is unable to initialize A20 properly - "ERROR: Unable to control A20 line" :
And there's no way to control it elsewhere in the BIOS setup; you'll have to clear the CMOS so that the instructions embedded in the chipset are no longer active and make HIMEM.SYS functional again :