Check if this amount is already maximum what the board takes. If all sockets are populated then _my guess_ is that this is maximum. Later boards featured SIPP's or SIMM's. Otherwise you have to use a memory upgrade board - usually quite expensive for what they are and it's a better option to buy a newer 286 board altogether.

There are empty sockets for mem modules. The BIOS Floppy installation disk states something about 4mb in total. I do not know if this is the case, as the menu tells me 4mb as an example. For me, something of 1 or 2 megabyte are fine enough on a 286.

In the manual, it is states that several upgrade kits of chips could be purchased back in 1987. Just not wich exact chips such kits were made of.

Post a picture of the board and it will make it easier to work out some solution, I haven't played with any 286 machines but from seeing people mess with these on youtube those sipp slots/sockets get lose and wear out over time but I know that one can replace the slots with simm slots. 4mb should be enough.

Yes, pictures. Does the chipset support EMS and/or UMB mapping? Otherwise DOS will only benefit from more memory through the HMA.

Well... I have misread the manual. It states that I can install "An additional of 1mb on the systemboard".
The system installation floppy disk, does however state 4 megabyte as an example.
I think that I will follow what the manual say, as this seems like the most correct answer. Anyway...
I will however post some pictures of the manual, as I have to take the whole system apart in
order to expose the motherboard. It is hidden below the HDD-mounting rails.
Will make another post with pictures of the manual.

h-a-l-9000 wrote:

Yes, pictures. Does the chipset support EMS and/or UMB mapping? Otherwise DOS will only benefit from more memory through the HMA.

That I do not know. The manual must give some answers I guess.

This is the complete Chaptor 6 in the manual.....
There is only 4 page's so I guess that I am missing some more in dept manual or something.
Hope this is at some help for you guys. 😀

If you Google <unisys "memory expansion kit">, one of the hits is this ancient PC Mag article which suggests the kit only provides an extra 1 MB. ("It does not support LIM 4.0" suggests we're talking about something with severely limited utility.) Maybe if you browse that issue, you'll find an ad with some useful part numbers?

One of the other hits is http://www.theprinterplace.com/parts/dataprod … re_parts12.html , but there's no way of telling what's what on that page. (It might just be printer parts, like it says.)

Guess:
20-pin are 44256 for 1MB.
18-pin are 4464 - to go from 512k to 640k, thus they should already be populated.
The soldered chips should be 16x 41256 for 512k.

Quite a mix 😀

Thanks.... I will look into this later, need to get some other project's finished first. 😀