Usually with those codes, excluding hardware problems, reprogramming the BIOS chip makes the PC work again, if you are interested on Tony359's YouTube channel there is the video on an ASUS Slot1, which after several repairs, he solved by reprogramming.
Here I would say that if you are able to do some investigations, I would go looking for something like interrupted track, bad welding, or defective SMD, maybe it could be somewhere the problem, then having found a way to make it work, it is a great clue, that there is something wrong, unfortunately I can't suggest a solution or where to focus the research.

impressive detective work
afaik ram detection happens on slowest safe chipset settings so nothing to be gained there, not to mention 0d means ram was detected and initialized successfully at this point

> code 41 0d

0D in this bios is Video bios execution

1seg000:F93D                 mov     al, 0Dh
2seg000:F93F                 mov     dx, 80h
3seg000:F942                 out     dx, al          ; manufacture's diagnostic checkpoint (POST code)
4seg000:F943                 mov     ax, 0C000h
5seg000:F946                 mov     ds, ax
6seg000:F948                 assume ds:nothing
7seg000:F948                 cmp     word ptr ds:0, 0AA55h
8seg000:F94E                 jz      short loc_FF971
9
10seg000:F971 loc_FF971:                              ; CODE XREF: seg000:F94E↑j
11seg000:F971                 push    bp
12seg000:F972                 call    far ptr 0C000h:3

41 is decompressing rest of the bios

1seg000:F977                 pop     bp
2seg000:F978                 mov     ax, 3
3seg000:F97B                 int     10h             ; - VIDEO - SET VIDEO MODE
4seg000:F97B                                         ; AL = mode
5seg000:F97D                 lea     ax, ds:0E000h
6seg000:F981                 mov     cx, 45h ; 'E'
7seg000:F984                 xor     dx, dx
8seg000:F986                 call    sub_FFAED
9seg000:F989
10seg000:F989 loc_FF989:                              ; CODE XREF: seg000:F96F↑j
11seg000:F989                 lea     ax, ds:0FEF8h
12seg000:F98D                 mov     cx, 17h
13seg000:F990                 nop
14seg000:F991                 mov     dx, 0FF01h
15seg000:F994                 call    sub_FFAED
16seg000:F997                 test    byte ptr [bp+0], 1
17seg000:F99B                 jz      short loc_FF9AB
18seg000:F99D                 lea     ax, ds:0FEBAh
19seg000:F9A1                 mov     cx, 19h
20seg000:F9A4                 nop
21seg000:F9A5                 mov     dx, 0FF01h
22seg000:F9A8                 call    sub_FFAED
23seg000:F9AB
24seg000:F9AB loc_FF9AB:                              ; CODE XREF: seg000:F99B↑j
25seg000:F9AB                 test    byte ptr [bp+0], 2
26seg000:F9AF                 jz      short loc_FF9BF
27seg000:F9B1                 lea     ax, ds:0FED3h
28seg000:F9B5                 mov     cx, 25h ; '%'
29seg000:F9B8                 nop
30seg000:F9B9                 mov     dx, 0FF01h
31seg000:F9BC                 call    sub_FFAED
32seg000:F9BF
33seg000:F9BF loc_FF9BF:                              ; CODE XREF: seg000:F9AF↑j
34seg000:F9BF                 mov     al, 41h ; 'A'
35seg000:F9C1                 mov     dx, 80h

PC@LIVE wrote on Yesterday, 19:27:

Usually with those codes, excluding hardware problems, reprogramming the BIOS chip makes the PC work again

sure looks like it! Either bios still corrupted (first 64KB), eprom A16 address line not connecting reliably, or bad ram that wasnt caught during ram detection? whatever it is its crashing during upper bios chip decompression

>After I accidentally shorted an output pin of a 74F244 with an input from the SiS496, and when powering off and on again, ¡the motherboard boots!

another impressive discovery 😮
which pin to which pin exactly?

rasz_pl wrote on Yesterday, 21:19:

impressive detective work afaik ram detection happens on slowest safe chipset settings so nothing to be gained there, not to men […]
Show full quote

impressive detective work
afaik ram detection happens on slowest safe chipset settings so nothing to be gained there, not to mention 0d means ram was detected and initialized successfully at this point

> code 41 0d

0D in this bios is Video bios execution

Copy code to clipboard

1seg000:F93D                 mov     al, 0Dh
2seg000:F93F                 mov     dx, 80h
3seg000:F942                 out     dx, al          ; manufacture's diagnostic checkpoint (POST code)
4seg000:F943                 mov     ax, 0C000h
5seg000:F946                 mov     ds, ax
6seg000:F948                 assume ds:nothing
7seg000:F948                 cmp     word ptr ds:0, 0AA55h
8seg000:F94E                 jz      short loc_FF971
9
10seg000:F971 loc_FF971:                              ; CODE XREF: seg000:F94E↑j
11seg000:F971                 push    bp
12seg000:F972                 call    far ptr 0C000h:3

41 is decompressing rest of the bios

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1seg000:F977                 pop     bp
2seg000:F978                 mov     ax, 3
3seg000:F97B                 int     10h             ; - VIDEO - SET VIDEO MODE
4seg000:F97B                                         ; AL = mode
5seg000:F97D                 lea     ax, ds:0E000h
6seg000:F981                 mov     cx, 45h ; 'E'
7seg000:F984                 xor     dx, dx
8seg000:F986                 call    sub_FFAED
9seg000:F989
10seg000:F989 loc_FF989:                              ; CODE XREF: seg000:F96F↑j
11seg000:F989                 lea     ax, ds:0FEF8h
12seg000:F98D                 mov     cx, 17h
13seg000:F990                 nop
14seg000:F991                 mov     dx, 0FF01h
15seg000:F994                 call    sub_FFAED
16seg000:F997                 test    byte ptr [bp+0], 1
17seg000:F99B                 jz      short loc_FF9AB
18seg000:F99D                 lea     ax, ds:0FEBAh
19seg000:F9A1                 mov     cx, 19h
20seg000:F9A4                 nop
21seg000:F9A5                 mov     dx, 0FF01h
22seg000:F9A8                 call    sub_FFAED
23seg000:F9AB
24seg000:F9AB loc_FF9AB:                              ; CODE XREF: seg000:F99B↑j
25seg000:F9AB                 test    byte ptr [bp+0], 2
26seg000:F9AF                 jz      short loc_FF9BF
27seg000:F9B1                 lea     ax, ds:0FED3h
28seg000:F9B5                 mov     cx, 25h ; '%'
29seg000:F9B8                 nop
30seg000:F9B9                 mov     dx, 0FF01h
31seg000:F9BC                 call    sub_FFAED
32seg000:F9BF
33seg000:F9BF loc_FF9BF:                              ; CODE XREF: seg000:F9AF↑j
34seg000:F9BF                 mov     al, 41h ; 'A'
35seg000:F9C1                 mov     dx, 80h

PC@LIVE wrote on Yesterday, 19:27:

Usually with those codes, excluding hardware problems, reprogramming the BIOS chip makes the PC work again

sure looks like it! Either bios still corrupted (first 64KB) or bad ram that wasnt caught during ram detection? whatever it is its crashing during upper bios chip decompression

>After I accidentally shorted an output pin of a 74F244 with an input from the SiS496, and when powering off and on again, ¡the motherboard boots!

another impressive discovery 😮
which pin to which pin exactly?

I hope 🤞 you want to share your discovery, even if it doesn't necessarily work on other motherboards, but I'd be curious to see if it's possible to fix the motherboard, and I don't know why it restarts with the error post codes.
Of course I would also suspect that the BIOS chip could have a defect, but thinking about it, it could be a pin with welding to be redone, it goes with the trick, and it doesn't go without it, maybe the trick bypasses the defective pin (?)

rasz_pl wrote on Yesterday, 21:19:

afaik ram detection happens on slowest safe chipset settings so nothing to be gained there, not to mention 0d means ram was dete […]
Show full quote

afaik ram detection happens on slowest safe chipset settings so nothing to be gained there, not to mention 0d means ram was detected and initialized successfully at this point

sure looks like it! Either bios still corrupted (first 64KB), eprom A16 address line not connecting reliably, or bad ram that wasnt caught during ram detection? whatever it is its crashing during upper bios chip decompression

>After I accidentally shorted an output pin of a 74F244 with an input from the SiS496, and when powering off and on again, ¡the motherboard boots!

another impressive discovery 😮
which pin to which pin exactly?

Yes, memory seems to be detected, because without any SIMM installed, the beeps are definitely different (continuous, but much longer) and the POST codes are totally different.

I checked continuity between all BIOS pins and the southbridge (85C497), directly from pins to pin (to avoid missing a false contact in the DIP socket or something). But I might consider reflowing at this point... I just tried to avoid reflowing the chipset as that operation is a bit risky and things can get worse.

The pins shorted were A2 (DRAM address line #2, coming out of a 74F244 and going to pin #14 of SIMM modules) and one of the chipset (85C496) outputs (either address line #5 or #6 seem to have worked, which corresponds to 85C496 pins #143 and #144).

This "trick" usually just hangs the motherboard and nothing more. Just sometimes (maybe one out of ten tries), the PC boots perfectly after next reset (to be precise: power down / power up the power supply).

PC@LIVE wrote on Yesterday, 21:32:

I hope 🤞 you want to share your discovery, even if it doesn't necessarily work on other motherboards, but I'd be curious to see if it's possible to fix the motherboard, and I don't know why it restarts with the error post codes.
Of course I would also suspect that the BIOS chip could have a defect, but thinking about it, it could be a pin with welding to be redone, it goes with the trick, and it doesn't go without it, maybe the trick bypasses the defective pin (?)

Sure! On my last post I already shared the shorted pins which sometimes allows the machine to boot.
I don't know how to reply to several users on the same post, so I posted this new post to reply to yours (please, let me know if there's a better way to do it).

I already tried 2 different BIOS chips (AT27C010) with two different binaries (the one that originally came with board, and the one on retroweb, which is: 03/14/96-SiS-496-497/A/B-2A4IB000C-00).
The behavior is identical 😳
That is, post code 41 0D, short continuous beeps, and I managed to boot at least one time with either them.

Also checks continuity of all pins to the southbridge 85C497. But, as I said in my previous post, maybe is time to reflow both big SMD chips. Just wanted to do everything possible before reflowing, as doing it can damage the board and make things worse.

The really weird thing is that the shortcircuit "trick" happens in the northbridge (between SIMM module and 85C496) but the BIOS is connected to the southbridge (85C497).
How could that short in northbridge bypass a defective pin in the other chip?
Not saying that is impossible.
But right now I cannot think on any (solid) explanation.

Just for fun, here's the replacement of the 74F244. It looks a bit messy, but it works just as well as the original SMD chip.

(The yellow adhesive tape is just kapton tape to protect components when desoldering the original SMD chip)

RetroVein wrote on Today, 10:15:

Sure! On my last post I already shared the shorted pins which sometimes allows the machine to boot. I don't know how to reply t […]
Show full quote

PC@LIVE wrote on Yesterday, 21:32:

I hope 🤞 you want to share your discovery, even if it doesn't necessarily work on other motherboards, but I'd be curious to see if it's possible to fix the motherboard, and I don't know why it restarts with the error post codes.
Of course I would also suspect that the BIOS chip could have a defect, but thinking about it, it could be a pin with welding to be redone, it goes with the trick, and it doesn't go without it, maybe the trick bypasses the defective pin (?)

Sure! On my last post I already shared the shorted pins which sometimes allows the machine to boot.
I don't know how to reply to several users on the same post, so I posted this new post to reply to yours (please, let me know if there's a better way to do it).

I already tried 2 different BIOS chips (AT27C010) with two different binaries (the one that originally came with board, and the one on retroweb, which is: 03/14/96-SiS-496-497/A/B-2A4IB000C-00).
The behavior is identical 😳
That is, post code 41 0D, short continuous beeps, and I managed to boot at least one time with either them.

Also checks continuity of all pins to the southbridge 85C497. But, as I said in my previous post, maybe is time to reflow both big SMD chips. Just wanted to do everything possible before reflowing, as doing it can damage the board and make things worse.

The really weird thing is that the shortcircuit "trick" happens in the northbridge (between SIMM module and 85C496) but the BIOS is connected to the southbridge (85C497).
How could that short in northbridge bypass a defective pin in the other chip?
Not saying that is impossible.
But right now I cannot think on any (solid) explanation.

Just for fun, here's the replacement of the 74F244. It looks a bit messy, but it works just as well as the original SMD chip.

The attachment 74F244 DIP.JPG is no longer available

(The yellow adhesive tape is just kapton tape to protect components when desoldering the original SMD chip)

Thank you very much for sharing this trick, for the moment as I had already written to you, I have not had a problem similar to yours, that's why normally after reprogramming the PC works again.
And as you wrote I would rule out a problem with the RAM, because I usually use RAM working heads, although there may be a doubt about some bad contact, but since you have found a way to make the PC work, I would say that your idea of redoing the chip welds, it could be possible that there is a PIN (or some?) That could have non-optimal contacts, before trying to renew the welds, I would try to hold the chip down and see if it can go beyond post code 41.
For multiple response no problem 😉, I do "reply" I select everything and copy, then I go back and do "reply" on the second user, and paste the selection of the first user, finally I add the answers for both users, it works but I can't tell you if it's right to do it that way.
Finally, on what the circuit or the BIOS does, when you use the trick, I don't know, I think there is a point where you jump over the post code 41, or maybe even if you find an error at 41, you can still continue.