weedeewee wrote on 2023-10-09, 20:03:

yes

Thanks, let's go spend some euros 😀

fyi, there might be other chips (e)eproms you can use, the 27c512 can only be re programmed after being erased with a UVC lamp.

weedeewee wrote on 2023-10-09, 20:57:

fyi, there might be other chips (e)eproms you can use, the 27c512 can only be re programmed after being erased with a UVC lamp.

Yes, i know that, i have few spares here, from old 486s. First under UV light, than reprogramming 😀

Today i managed to flash v2.7 BIOS, but the problem remains. Max 8MB RAM can be seen on this motherboard! Is it problem in my RAM sticks or what? Those sticks works without any issue on other motherboard. I will try to flash this v2.11 version, but i doubt it will change anything. Anybody have a clue what could be wrong?
Thanks

broken/cracked address line, one of the higher ones. A11 or A10. Just guessing.

weedeewee wrote on 2023-12-01, 21:16:

broken/cracked address line, one of the higher ones. A11 or A10. Just guessing.

I could try to find visible cracked traces on microscope if that what You thinked?

yes,
or check for continuity first on
pin 19 & 24 ( https://pinoutguide.com/Memory/Simm30_pinout.shtml )
to
U29 ( the big chip in the top right corner of the board ) https://theretroweb.com/motherboard/image/386 … 52287346678.jpg ) no idea which pins exactly.

weedeewee wrote on 2023-12-02, 08:51:

yes, or check for continuity first on pin 19 & 24 ( https://pinoutguide.com/Memory/Simm30_pinout.shtml ) to U29 ( the big chi […]
Show full quote

yes,
or check for continuity first on
pin 19 & 24 ( https://pinoutguide.com/Memory/Simm30_pinout.shtml )
to
U29 ( the big chip in the top right corner of the board ) https://theretroweb.com/motherboard/image/386 … 52287346678.jpg ) no idea which pins exactly.

Thanks a lot, i will do that today definitely!!! I hope this will make me smile 😀

butjer1010 wrote on 2023-12-02, 09:59:

weedeewee wrote on 2023-12-02, 08:51:

yes, or check for continuity first on pin 19 & 24 ( https://pinoutguide.com/Memory/Simm30_pinout.shtml ) to U29 ( the big chi […]
Show full quote

yes,
or check for continuity first on
pin 19 & 24 ( https://pinoutguide.com/Memory/Simm30_pinout.shtml )
to
U29 ( the big chip in the top right corner of the board ) https://theretroweb.com/motherboard/image/386 … 52287346678.jpg ) no idea which pins exactly.

Thanks a lot, i will do that today definitely!!! I hope this will make me smile 😀

I too, hope so.

weedeewee wrote on 2023-12-02, 08:51:

yes, or check for continuity first on pin 19 & 24 ( https://pinoutguide.com/Memory/Simm30_pinout.shtml ) to U29 ( the big chi […]
Show full quote

yes,
or check for continuity first on
pin 19 & 24 ( https://pinoutguide.com/Memory/Simm30_pinout.shtml )
to
U29 ( the big chip in the top right corner of the board ) https://theretroweb.com/motherboard/image/386 … 52287346678.jpg ) no idea which pins exactly.

Something is weird here! There is no continuity between U29 and any address line?!? Only data lines have continuity with U29. I tried all the address lines, from 0 to 11, but none of them does have continuity with U29! I don't think that all the traces are broken 😀

[/quote]
I too, hope so.
[/quote]

Do You have any idea where to check next?
Thanks in advance

figure out where the address lines are connected .

weedeewee wrote on 2023-12-06, 05:42:

figure out where the address lines are connected .

OK, will try 😀

from the photos I think pin 19 on the sim socket is connected to pin 96 of the big chip between the cpu & isa slots. I'd expect the other one to be nearby.

weedeewee wrote on 2023-12-06, 15:23:

from the photos I think pin 19 on the sim socket is connected to pin 96 of the big chip between the cpu & isa slots. I'd expect the other one to be nearby.

Pin 19 is connected to the U18 (near cache chips), 12th pin i guess (3rd from below right).
Pin 24 i cannot find where it goes. I have one M321 that was beyond repair (Battery acid destroyed it), and i took down the memory slots, and it doesn't have any visible traces from upper or lower side of the PCB. Probably the trace is going between layers 🙁
Picture shows where goes PIN 19 trace

Just 2 cents.

I have the same board, i have MR-BIOS on it (THE BEST BIOS!!!) and i run it with 8x4MB SIMMs. The SIMM modules are 3-chip variants, so with higher density chips. Works perfectly.
I didn't have any memory issues with original bios either.

So just make sure that you don't have any damage between chipset and RAM sockets. Also, sometimes boards may behave weirdly, regarding the RAM, when the real issue is with cache. (Settings or damage or whatever) So make sure everything related to cache is also in good order.

Nevermind the 24 (A11) then, I think it's only used for 16MB simms and the board doesn't support those, so it's likely there is no trace whatsoever.
On the backside photo of the board I see pin 19 (A10) is linked for four slots, but seperate and linked for the other four slots.

The datasheet for the 74f86n tells us pin 3 is an input output for an XOR or gate. It should be connected somewhere else as well.

Since 1MB simms are working, try to figure out where pin 18 (A9) from the simm slots goes to.
It's also possible it goes to multiple locations, so if you find one continuity, keep looking for a possible other location.

GigAHerZ, thanks for the input. Always good to have another pov.

edit: the other bank is connected to pin 6 of the 74f86n, which is also an output for an XOR or gate.
pin 1 & 2 are the inputs for pin3, pin 4 & 5 are the inputs for pin 6
It could be that the chip 74f86 is defective, or that a trace of its input is broken somewhere.

GigAHerZ wrote on 2023-12-06, 18:21:

Just 2 cents. […]
Show full quote

Just 2 cents.

I have the same board, i have MR-BIOS on it (THE BEST BIOS!!!) and i run it with 8x4MB SIMMs. The SIMM modules are 3-chip variants, so with higher density chips. Works perfectly.
I didn't have any memory issues with original bios either.

So just make sure that you don't have any damage between chipset and RAM sockets. Also, sometimes boards may behave weirdly, regarding the RAM, when the real issue is with cache. (Settings or damage or whatever) So make sure everything related to cache is also in good order.

I did add 128KB cache more than the original state! So it could be problem with cache? I will try to revert to 128kB and check! Thanks

weedeewee wrote on 2023-12-06, 18:26:

Nevermind the 24 (A11) then, I think it's only used for 16MB simms and the board doesn't support those, so it's likely there is […]
Show full quote

Nevermind the 24 (A11) then, I think it's only used for 16MB simms and the board doesn't support those, so it's likely there is no trace whatsoever.
On the backside photo of the board I see pin 19 (A10) is linked for four slots, but seperate and linked for the other four slots.

The datasheet for the 74f86n tells us pin 3 is an input output for an XOR or gate. It should be connected somewhere else as well.

Since 1MB simms are working, try to figure out where pin 18 (A9) from the simm slots goes to.
It's also possible it goes to multiple locations, so if you find one continuity, keep looking for a possible other location.

GigAHerZ, thanks for the input. Always good to have another pov.

edit: the other bank is connected to pin 6 of the 74f86n, which is also an output for an XOR or gate.
pin 1 & 2 are the inputs for pin3, pin 4 & 5 are the inputs for pin 6
It could be that the chip 74f86 is defective, or that a trace of its input is broken somewhere.

Yes, pin 19 is going to 74f86 (U18 as i stated in last post), so, i will try to change cache amount like GigAHerZ stated, or i will try to replace 74f68 from this other board!
Thanks again....

butjer1010 wrote on 2023-12-06, 18:57:

GigAHerZ wrote on 2023-12-06, 18:21:

Just 2 cents. […]
Show full quote

Just 2 cents.

I have the same board, i have MR-BIOS on it (THE BEST BIOS!!!) and i run it with 8x4MB SIMMs. The SIMM modules are 3-chip variants, so with higher density chips. Works perfectly.
I didn't have any memory issues with original bios either.

So just make sure that you don't have any damage between chipset and RAM sockets. Also, sometimes boards may behave weirdly, regarding the RAM, when the real issue is with cache. (Settings or damage or whatever) So make sure everything related to cache is also in good order.

I did add 128KB cache more than the original state! So it could be problem with cache? I will try to revert to 128kB and check! Thanks

Really? from the photo you posted with the trace of A10 I would've sworn you have only 64Kilobyte of cache on the board.
edit: oh well, maybe that's the other board you have. 😀