Before doing anything else you shoudl remove the battery 😉

Maybe you are able to upgrade to 640k by adding an identical chip to the empty socket on the bottom left.

But you should be able to add an additional 4MB with 4 SIPP-modules. Maybe there is a jumper to switch between banks, just try all of them 😉

Have you tried this website?
http://arvutimuuseum.ee/th99/

I second the battery removal. Also, good chance that it will auto detect the RAM in the SIPP sockets. Stason TULARC didn‘t have this specific board either, I think. Any markings or stickers on the back?

Look at #26 here:
80286 BIOS image collection
This one has 1 MB.

I think you only need to add 1 single chip to get 1 MB. The empty small sockets on the bottom right are parity I guess.

Predator99 wrote:

Before doing anything else you shoudl remove the battery 😉

Although the battery is working properly (the mobo saves the date/time/settings OK) , Yes, I'm going to change it tomorrow. It's planned

Predator99 wrote:

Maybe you are able to upgrade to 640k by adding an identical chip to the empty socket on the bottom left.

But you should be able to add an additional 4MB with 4 SIPP-modules. Maybe there is a jumper to switch between banks, just try all of them 😉

Where can I get that chips or better, where can I get SIPP-modules?

SIPP will be tough. But you can take 30pin SIMM modules and solder pins to them...

jesolo wrote:

Have you tried this website?
http://arvutimuuseum.ee/th99/

I searched for in statong.org and I found similar boards, but not identical:

https://stason.org/TULARC/pc/motherboards/U/U … HT101A-286.html
https://stason.org/TULARC/pc/motherboards/U/U … 286-GH-286.html
https://stason.org/TULARC/pc/motherboards/U/U … MAIN-BOARD.html

root42 wrote:

I second the battery removal. Also, good chance that it will auto detect the RAM in the SIPP sockets. Stason TULARC didn‘t have this specific board either, I think. Any markings or stickers on the back?

Yes

root42 wrote:

SIPP will be tough. But you can take 30pin SIMM modules and solder pins to them...

Are you shure?
https://www.ebay.com/sch/i.html?_odkw=zipp+me … odules&_sacat=0

jesolo wrote:

Have you tried this website?
http://arvutimuuseum.ee/th99/

I just looked and it is not there

brostenen wrote:

root42 wrote:

SIPP will be tough. But you can take 30pin SIMM modules and solder pins to them...

Are you shure?
https://www.ebay.com/sch/i.html?_odkw=zipp+me … odules&_sacat=0

Not 100% sure, but I think you need to populate all 4 banks at once?

Think my proposal to add the 8. chip is the most cost effective solution to get more RAM. Dont see the kind of the chips on the photo, but 4 of these are 512kb (which are detected) and the other 3 are currently unsused.

brostenen wrote:

root42 wrote:

SIPP will be tough. But you can take 30pin SIMM modules and solder pins to them...

Are you shure?
https://www.ebay.com/sch/i.html?_odkw=zipp+me … odules&_sacat=0

Ok, wrong formulation: for the price of one SIPP module, I got four SIMM modules. I think the latter were much more ubiquitous. 😀

Predator99 wrote:

brostenen wrote:

root42 wrote:

SIPP will be tough. But you can take 30pin SIMM modules and solder pins to them...

Are you shure?
https://www.ebay.com/sch/i.html?_odkw=zipp+me … odules&_sacat=0

Not 100% sure, but I think you need to populate all 4 banks at once?

Think my proposal to add the 8. chip is the most cost effective solution to get more RAM. Dont see the kind of the chips on the photo, but 4 of these are 512kb (which are detected) and the other 3 are currently unsused.

Hi again!!

I've token some pictures more closely of the chips: all chips are equals: mb81c4256-80p

I understand the motherboard has 512kb in a bank and 384 Kb in another bank. 512 kb is running but the other 384 kb is deactivated. If I buy a mb81c4256-80p and it plugs in the socket in the left botton corner and I modify the jumpers it should be 1mb the ram. is it right?

The other solution, SIPP modules, I think it's very more dificult becuase the motherboard has not label for the pin 1

muon wrote:

Hi again!!

I've token some pictures more closely of the chips: all chips are equals: mb81c4256-80p

I understand the motherboard has 512kb in a bank and 384 Kb in another bank. 512 kb is running but the other 384 kb is deactivated. If I buy a mb81c4256-80p and it plugs in the socket in the left botton corner and I modify the jumpers it should be 1mb the ram. is it right?

Yes. You dont need exactly the mb81c4256-80p, there are many compatible ones...google. Dont think you have to modify jumpers for this upgrade.

Other solution:
These cards:
ISA XMS/EMS Memory Extension / Expansion cards: Now Running without Driver / Documentation :-)
..but I think they are even harder to get...

Hi Predator99!!

The Chips were received a few days ago. I tested yesterday... and YES I plugged one chip in the empty socket and I get 1024 KB of memory .

Now I have got another problem with the board. Here:
Right orientation SIPP module in 286 motherboard?

Sorry to dig up this old thread, but I've just ended up with a 286 that has the same motherboard (with minor differences, e.g. the CPU is Siemens branded). Back is also marked VLSI-4A 90501. It's in great shape, no battery leakage (I will remove it of course). It works and was installed so I at least know where the reset/power/speaker/turbo should go.

I assume the OP didn't find out any further info on it?

If anyone else ever does, please post here!

Can you dump its bios please ? There might be useful information in there 😀

Hello Deksor. I did attempt to but the PROMS are not UV EPROMS, they are marked SDL128 and R3 T002 (both are the same I assume, but so far I've only lifted one sticker). I think the '128' part probably indicates a 27128/27C128 so I tried a couple of well known brands but it reported wrong/bad pins when trying to read.

So if you have any info on those and a suitable compatible chip to select on my Eprom programmer I will read and dump right away.

Oh, by the way, the BIOS boot screen says it's v3.03HL from Award Software Inc.

Since your board boots, you can use this 😀 http://cd.textfiles.com/microhaus/mhblackbox3 … MORY/GETROM.ZIP