Search for HYB511000 but there are others

You have 2 banks of 512K each, which should be treated as 512+512 or 640+384, not 512+0. It seems the memory in bank 1 is not correctly recognized. Possibly one of the chips is broken.

The Chip numbers printed on the board are generic, and many chips have slightly or considerably different naming schemes. For example, your V53C104 chips are called 414256 in the silkscreen. If you want to go full 4MB, you need 36 chips, each of them "1M x 1". Examples for this kind of memory chips are Fujitsu MB81C1000A, NEC µPD421000C (often spelled UPD421000C), MCM511000A. Searching for "1M x 1" DRAM DIP should yield enough results to find offers for the chips you need.

Not sure if this is helpful, but CheckIt by TouchStone has a diagnostic option for the memory banks.
It's intended to physically track down faulty memory chips.

btw I have the same 😉

Re: 80286 BIOS image collection

Can you dump your BIOS please?

Most old motherboards do not automatically detect ram and required a bios program to be run off a disk to set the ram size.

There are a few generic utilities around

Also, slightly newer “old” motherboards would again not detect ram and require the size set in the bios itself

If you can find no way to enter the bios during post you will need a utility to set your bios parameters from dos

Occasionally some boards did allow you to choose how much “base” memory there was via jumper(s) but that likely isn’t the case here.

Predator99 wrote on 2021-09-04, 19:33:

btw I have the same 😉

Re: 80286 BIOS image collection

Can you dump your BIOS please?

Not sure how to do that 😀

mkarcher wrote on 2021-09-04, 19:14:

You have 2 banks of 512K each, which should be treated as 512+512 or 640+384, not 512+0. It seems the memory in bank 1 is not correctly recognized. Possibly one of the chips is broken.

The Chip numbers printed on the board are generic, and many chips have slightly or considerably different naming schemes. For example, your V53C104 chips are called 414256 in the silkscreen. If you want to go full 4MB, you need 36 chips, each of them "1M x 1". Examples for this kind of memory chips are Fujitsu MB81C1000A, NEC µPD421000C (often spelled UPD421000C), MCM511000A. Searching for "1M x 1" DRAM DIP should yield enough results to find offers for the chips you need.

Thanks, will check your info later!

Jo22 wrote on 2021-09-04, 19:23:

Not sure if this is helpful, but CheckIt by TouchStone has a diagnostic option for the memory banks.
It's intended to physically track down faulty memory chips.

I assume that such software is useful when RAM is recognized by BIOS?!

aknot wrote on 2021-09-04, 22:06:

Predator99 wrote on 2021-09-04, 19:33:

btw I have the same 😉

Re: 80286 BIOS image collection

Can you dump your BIOS please?

Not sure how to do that 😀

Please install "NSSI". There is a option to dump the system BIOS to a file
https://www.navsoft.cz/products.htm

When you take a look at my board: I have the same RAM config as you have and 1MB is detected. So yes, your BIOS setting may be wrong. You can also try testx
download/file.php?id=100469
It tests the installed RAM and doesnt care about what the BIOS reports.

Predator99 wrote on 2021-09-04, 22:19:

Please install "NSSI". There is a option to dump the system BIOS to a file https://www.navsoft.cz/products.htm […]
Show full quote

aknot wrote on 2021-09-04, 22:06:

Predator99 wrote on 2021-09-04, 19:33:

btw I have the same 😉

Re: 80286 BIOS image collection

Can you dump your BIOS please?

Not sure how to do that 😀

Please install "NSSI". There is a option to dump the system BIOS to a file
https://www.navsoft.cz/products.htm

When you take a look at my board: I have the same RAM config as you have and 1MB is detected. So yes, your BIOS setting may be wrong. You can also try testx
download/file.php?id=100469
It tests the installed RAM and doesnt care about what the BIOS reports.

Hello,

Tried to use "NSSI", but it crashes with error 0-0-2-215-1-0DBA:1C4D, is there a similar tools?
"testext" shows no extended memory...

I believe this is EM related issue. So need to solve it, then I will be able to dump the BIOS.

Hello,

Good news everyone! After some test I found that one leg of the socket for RAM chip is damaged by corrosion. So new sockets are soldered and now RAM is working as expected 😀 Will dump bios as soon I will have a time for it 😀 Thanks for the help!

Hello,

Here is BIOS of mother board and VGA.
Now I have another issue 😀 Turbo switch. Display reports 16Mhz, but diagnostics show 8Mhz. If I disable turbo, PC doesn't even starts. Maybe someone could help with correct jumper settings for board (picture attached)?

Thanks in advice!

Nice Motherboard 😀 And NIce VGA Card possible the slowest Card ever made 😁

matze79 wrote on 2021-10-22, 18:10:

Nice Motherboard 😀 And NIce VGA Card possible the slowest Card ever made 😁

This poor granny was in very bad condition. So be respectful 😀 a few things left to finish this project, but now I'm stuck with this turbo thing...

Thanks for the dump, I have added it here
Re: 80286 BIOS image collection

I assume that issue is not related to "turbo switch board". If "TURBO" pins are open motherboard is not get POST BEEP, if pins are shorted it BEEPs ok and shows 8Mhz with diagnostic tool. Any ideas what could cause such behavior? Of course if my assumption that shorted TURBO pins enables TURBO 16Mhz is right.

Thanks,

aknot wrote on 2021-10-22, 19:06:

I assume that issue is not related to "turbo switch board". If "TURBO" pins are open motherboard is not get POST BEEP, if pins are shorted it BEEPs ok and shows 8Mhz with diagnostic tool. Any ideas what could cause such behavior? Of course if my assumption that shorted TURBO pins enables TURBO 16Mhz is right.

Thanks,

Your BIOS has a "Speed Select" setting - No Change, Low, or High. How do you have that set?

Your BIOS has a "Speed Select" setting - No Change, Low, or High. How do you have that set?

Tried to play with these settings as well. The same behavior.

Broken or faulty contact on one of the oscillators ? looks like you've got two, one I assume 16 MHz, divided by two would give the 8MHz cpu speed, and one 32MHz which would deliver the 16MHz.
One of the ceramics around them could also be at fault.