I think the small ones are for parity, you can try without them. I would suggest to remove half of the big ones and test with 512 Kb in two runs to see where the error is located.

Great suggestion! Thanks! To use half the memory, should I take out a column or two rows (if that makes sense)?

Think a row corresponds to a Bank. Just try you cannot damage anything.

Wrong.. See the bold white lines around 6 ICs? This will correspond to a Bank.

Apart from potential hardware problems, hanging etc, it will report only 640KB if shadowing (or whatever it's called in its BIOS) is enabled 😉 The same way it'll report 3712 with 4MB.
1024KB - 384KB = 640KB

Eagle eyes!

OK. This is what I will try. I will remove the 4 smaller ones and remove the top bank. If that equates to 512Kb then I will switch out the bank with the ones from the the top bank. If one is kapot, it should equate to less memory reported in either try. If both times it reports 512Kb then there might be a problem with the smaller ones?

PS: I will also run a full memory test for each bank, actually maybe that might help me pin point which one is broken if I can somehow find out which memory address maps to which chip...

@konc I'm pretty sure any of those BIOS options where Disabled, but I will check, just to be sure.

@Predator99 It even says "Bank 0" and "Bank 1" on the right hand side... Facepalm... 😀

I will first use the Bank 0 sockets for testing, then do the same tests on Bank 1. Could be that one there is a problem with one of the sockets?

I expect that Bank 0 needs to be populated and Bank 1 will not run alone. What board is this? Full picture?

Right click and open in new tab to get 100% view.

Nice!
Have some similar boards here
80286 BIOS image collection
Add yours if you like. Will be cheaper to upgrade memory with simm. I assume 4 MB are supported that way.

Very nice! That's quite a collection. I see you have an Olivetti board. Awesome. I had two Olivetti's growing up in the early nineties, an M24 (8086) and an Olivetti PC S286, both thrown out by my mother a few years after I moved out of the house. I'm sure you can imagine the shock when I found out...!

I did try 4 x 1meg sticks in my board but it wasn't recognising them either, that's the next thing to focus on once I've sorted out the main memory. Won this board in an eBay auction for $50 USD. Pretty reasonable..., I think... 😀

This board of yours seems to have some similarities to mine:

Nice!

Yes price is quite ok. Didnt keep all boards listed there. You will have to switch a Jumper to use simm.

Ah OK. So you can't use the on-board memory and the simm memory at the same time... The only jumper I can think of that might be eligible for simm memory switch would be JP2 (an open 3 pin header which sits next to the co-processor). I have a manual of a similar board and in that manual that location is JP3 and allows you to select NPU mode synchronous/asynchronous with CPU.

https://stason.org/TULARC/pc/motherboards/U/U … LAND-286GV.html

I'm not sure if that applies to simm memory...

Also, I have since I've taken the photos, installed a 80287 and I noticed that it gets quite hot, even after only 10 mins or so while the other chips (like the main cpu) isn't nearly as hot. Do you happen to know if this is normal?

PS: For completeness, these are my jumpers:

(bottom of the board along the DIP memory)

JP3 - 3 pin, NOMO COLOR (2 & 3 closed)
JP4 - 2 pin, TRSW (closed)
JP5 - 5 pin, KEYLOCK POWER LED (open)
JP? - 2 pin, TR LED (open)
JP7 - 4 pin, SPEAKER (I have a speaker attached)

Then there is:

JP2 - 3 pin, this JP3 in the manual linked (open).

The only other jumper like header is the external battery connector near the keyboard connector.

How fast is your 287? 8 MHz? In asynchronous mode your 286 has 16 MhZ and FPU 10 MHz (?). In synchronous mode both 16 MHz which might be too fast?

Ah OK. Well, since JP2 (my board) isn't closed at all, I'm not sure what "mode" it's in (it seems to detect the FPU though, I see it during boot). I assume then when a FPU is installed that either of the 2 modes should be selected?

This is the 287 I got, $20 USD (for an allegedly new, it looks new though):

https://www.ebay.com.au/itm/163351190006

It's says: C80287-3, not sure what the "3" refers to, the mhz?

PS: The idea is to fully pimp out this board. Unfortunately it only seems to take up to 4mb, would have loved a 16mb, 16Mhz 286 with an FPU. 😀

Yes, think its 3MHz - you shouldnt use it in that board.

Most (all?) 286 Boards have max. 4MB. You need an expansion card for more.

Great! Thanks for the heads up, much appreciated!

Oh, maybe for the simm memory to work, the DIP memory shouldn't be installed, could that be an option? I mean, there doesn't seem to be an explicit jumper.

pan069 wrote:

This is the 287 I got, $20 USD (for an allegedly new, it looks new though):

https://www.ebay.com.au/itm/163351190006

It's says: C80287-3, not sure what the "3" refers to, the mhz?

Beautifully, but ancient FPU! The ceramic / gold casing points really to an old FPU. I also never saw a 3 MHz variant. I think this is more a collector's item. You will easily find an AMD 287 / 8 MHz. They were rather common.

Update: the 80287-3 is indeed the 6 MHz version:

https://en.wikipedia.org/wiki/X87#/media/File … ntel_C80287.jpg

Which is probably to be used with 8MHz 80286s. The 80287 usually has an internal 2/3 clock divider.