The HT12 only supports 4M (4x1M 30p) of RAM total. so A10 & A11 would have no need to be connected to any simm slot.

Rafal wrote on 2021-08-20, 08:40:

Predator99 wrote on 2021-08-18, 14:27:

Did you search for 514256 ...think they should work? You can also look on old VGA cards for some matching ones...

I was looking for HY534256S-70, saw another thread on forum with a mobo with these chips. Also it has a smaller DIP16 chips, i guess these are for parity? Do i need the DIP16 or Its just enough to fill one bank with DIP20?

They are identical, see here:
http://www.knubbelmac.de/hardware/ram-kalkulator.html

Yes, the DIP16 are for parity. I am not 100% sure, but I think these are optional - at least if you have a jumper to disable parity.

Rafal wrote on 2021-08-20, 08:40:

I did just a quick check with a DMM and it turns out that more address traces are not connected to the chipset. So I made a clos […]
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I did just a quick check with a DMM and it turns out that more address traces are not connected to the chipset. So I made a closer look but I see no other damage (I already fixed one tiny address line break before).
For example the A10 is not connected to HT12, and does not beep on any of the DIP sockets aswell. I need to take closer look and maby make some bridges, but still don't know where exactly...
But in general, it should just like you wrote:
- address from CPU to HT12 (green)
- memory address (MA?) from HT12 to RAM (blue)
- data CPU, HT12, RAM (red)

You are right, MA means "memory address". That's a commonly used abbreviation for address busses where column/row is already multiplexed. As weedeewee said, don't bother about A10. A10 is the eleventh address bit (remember that counting starts at A0), so if you use A10, you have 11 row + 11 column address bits, resulting in 22 address bits in total, which is 4M. The HT12 chipset doesn't support 4MB SIMMs, so it doesn't have A10 at all. A9 is used only on 1MB SIMMs / SIPPs, but not on 256K SIMMs/SIPPs. If any bit of A0 to A8 doesn't get a proper signal from the chipset, something is wrong and needs to be fixed.

So she's finally alive!

After I installed the memory that came, I had the board working for one time, but then I got the same parity or it kinda booted but soon after the "American Megatrends" logo it then displayed "CMOS INOPERATIONAL SYSTEM HALTED".
So I've read some threads here about regenerating old dallas chips and using them in 286 boards... so I did and it worked right away. It stores the settings, and it runs to the boot screen.

Unfortunately my know-working IDE/FDD controller refuses to work with this board, kinda bummer (everything connectred properly, and FDD light always ON, HDD not booting, when there is a SD->CF adapter then no boot at all). I will try another IO card other day.

As for now I post the photos of this success, it wouldn't be without you guys, thank you all so much!

Rafal maybe you have bios files for this motherboard or You can write ident number (bottom of boot screen) . I have the same motherboard without the original bios. Only the bios from "eurosoft ver4.71" started the board, but not quite correctly

Hi Tomasz, on the photo, there is the bios ident number. I do not have those files.

Rafal wrote on 2022-01-14, 23:12:

...FDD light always ON, HDD not booting, when there is a SD->CF adapter then no boot at all..

I also have a very early 486 that really doenst like to post / boot with a CF card on ide. With a normal 350MB HDD it boots fine. I dont know yet if its the controller or the board...
A permanent floppy light would indicate to me the data cable is plugged in backwards.