I assume all the DIP sockets are empty? Have you tried only 2 sticks (since 286 only has 16-bit bus you need only 2x8 to boot) in either bank 2 or 3?
If the setting page you found is correct you can use 2x256k in either bank (or both) but only 2x1M in bank 2 will work (or both banks but it's not working for you ATM).

If that doesn't help, dig out some datasheets and check:
1) within a bank the address lines should be connected to both slots in the same spots, but not data lines
2) that depends on the chipset but I'd venture a guess that data lines go directly to the CPU so test that, it should be lower (D0-D7) and upper byte (D8-D15) for each slot
3) if data lines are connected to the CPU then they should also be connected to each other in banks, and also the DIP sockets
4) DIP socket address and data lines should connected to the SIMM slots, but the actual mapping might be confusing
5) the switch most likely connects to the control lines and routes them either to SIMM or to DIP - find pinouts for your typical 44256 and 30-pin SIMM and compare

Chances are you have a broken trace, either data or address, because 512k in SIMM is not even valid configuration. Problem is, the CPU address lines don't go to RAM directly but through a mobo chip (x86 family can't natively talk to RAS/CAS addressed DRAM, nor does it do refresh on it's own). So if the problem is between CPU and the chipset - you might not be able to easily find it...

I second that. Once the PC can boot, try to run the usual mainboard tests of CheckIt!, NSSI, Dr.Hardware, SI and how they are all called.
Perhaps it's nothing, but maybe the Keyboard Controller has some issues, too.
If you can, remove it gently from the mainbaord and check if the socket has good contacts.
A corred/leaked battery is often near the KBC socket, so there might be some broken traces in that area.

Edit: Some mainboards have custom PAL/GAL chips (16xxx ?) that perform addressing stuff..
Perhaps unrelated, but please visually check if they look fine (these chips often have stickers on them and are very tiny).

Deunan wrote:

I assume all the DIP sockets are empty? Have you tried only 2 sticks (since 286 only has 16-bit bus you need only 2x8 to boot) i […]
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I assume all the DIP sockets are empty? Have you tried only 2 sticks (since 286 only has 16-bit bus you need only 2x8 to boot) in either bank 2 or 3?
If the setting page you found is correct you can use 2x256k in either bank (or both) but only 2x1M in bank 2 will work (or both banks but it's not working for you ATM).

If that doesn't help, dig out some datasheets and check:
1) within a bank the address lines should be connected to both slots in the same spots, but not data lines
2) that depends on the chipset but I'd venture a guess that data lines go directly to the CPU so test that, it should be lower (D0-D7) and upper byte (D8-D15) for each slot
3) if data lines are connected to the CPU then they should also be connected to each other in banks, and also the DIP sockets
4) DIP socket address and data lines should connected to the SIMM slots, but the actual mapping might be confusing
5) the switch most likely connects to the control lines and routes them either to SIMM or to DIP - find pinouts for your typical 44256 and 30-pin SIMM and compare

Chances are you have a broken trace, either data or address, because 512k in SIMM is not even valid configuration. Problem is, the CPU address lines don't go to RAM directly but through a mobo chip (x86 family can't natively talk to RAS/CAS addressed DRAM, nor does it do refresh on it's own). So if the problem is between CPU and the chipset - you might not be able to easily find it...

I tried with only 2 sticks but even if I put in 2x 1MB sticks it still only recognizes 512kb. Even after editing the correct memory size in BIOS.
I also checked the board for damage but the only damage is one of the memory retaining clips is partly broken off. The bank is recoginized and works, if I only put memory in those slots it still is detected, albeit always as 512kb.

I am not that great with the chipset and specs sheets. The chipset is a CHIPS P82C211-P82C215 type with multiple chips. The P82C212B-12 A chip seems to have multiple lines going to atleast the RAM slots, but all legs are straight and if a look with a magnifying glass all joints seem good.

Jo22 wrote:

I second that. Once the PC can boot, try to run the usual mainboard tests of CheckIt!, NSSI, Dr.Hardware, SI and how they are a […]
Show full quote

I second that. Once the PC can boot, try to run the usual mainboard tests of CheckIt!, NSSI, Dr.Hardware, SI and how they are all called.
Perhaps it's nothing, but maybe the Keyboard Controller has some issues, too.
If you can, remove it gently from the mainbaord and check if the socket has good contacts.
A corred/leaked battery is often near the KBC socket, so there might be some broken traces in that area.

Edit: Some mainboards have custom PAL/GAL chips (16xxx ?) that perform addressing stuff..
Perhaps unrelated, but please visually check if they look fine (these chips often have stickers on them and are very tiny).

The board works if booted, tests work OK, keyboard also works well.
To be sure I just reseated it, the CPU also without making a difference.
Battery is flat, but 0 leakage so thank god that is not the issue. I plan on connecting an external pack later, which currently is in my 486 system.

Regarding the PAL/GAL chips, I will post a good picture ASAP of the board, perhaps somebody will find something on that.

I had an older 286 that required you to run a bios program when you changed the memory quantity,
You had to manually enter the amount of base and extended memory save and exit.
If memory serves the Simms could only be used as extended memory which meant weird things since it only had 512kb of base memory.

Does your bios see how much ram you have?
Or is it a field you fill out?

Well, after alot of things happened I finally had some time again today. I added an external battery to the board, switched the jumper for this and tried all combinations possible.
Time was now saved by the board, the 1.44 mb floppy too, but whatever I do the board switches always back to 512kb and complains the memory configuration is wrong.
Even if I select 512kb the board complains it is not good… 😒

I filled up all slots (4x 256kb 30 pins and 2x 512kb in de dip sockets) and tried.. but whatever I tried always the complaint it is incorrect..
Only thing I can imagine is that the bios itself has an issue. It is the DTK bios 3.09 for 286.
I found a 3.18 version but I have no ROMs and no burner so I cannot test if this resolves the issue. Perhaps in the future. For now the board goes into the lot of half working boards.

What happens if you remove all memory?

Are the dips hard wired to bank zero?

Could you install only Simms and no dipps?

Might be a bad trace, solder joint or even memory,

Who knows without more troubleshooting

rmay635703 wrote:

What happens if you remove all memory? […]
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What happens if you remove all memory?

Are the dips hard wired to bank zero?

Could you install only Simms and no dipps?

Might be a bad trace, solder joint or even memory,

Who knows without more troubleshooting

Dips are bank 0 and bank 1.
If I install only Simms and no dipps then exactly the same happens.
All the simm memory I am using to test works in other 386 systems without problems.
That is the frustrating part, I can also continue with a startup floppy and everything works but I stay limited to 512kb..