Welcome and Hmm ok. Are the 30pin SIMMS 3 chip or 9 chip ? It does make a difference.
Being an OEM board w/o a manual can make it very hard to decode... first you need to set the jumpers proper and then set the bios ram settings to match the ram+what you want.
After a quick search found this: https://theretroweb.com/motherboards/s/kaimei-kma-202f-12r
Same chipset and general layout but in AT style (not LPX like yours), good thing is the jumpers by ram and 83c203 have exact same number of jumpers. I suggest you try what it's manual says...
So those jumpers (jp14,15,16?) by 83c203 need all be jumped for 640k + 3328k Extended + 128k shadow (yes you want that). And for SIMMS you want JP8-13 to be jumped as 1-2 as in your picture.
added: If you set those jumpers by 83c203 same as picture it is wrong for 4 x 1MB simms !
In the BIOS you may need to mirror those 640k + 3328K +128k settings...
If you can post a picture of the BIOS memory settings page it would help.

Horun wrote on 2024-07-30, 03:55:

Welcome and Hmm ok. Are the 30pin SIMMS 3 chip or 9 chip ? It does make a difference. Being an OEM board w/o a manual can make […]
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Welcome and Hmm ok. Are the 30pin SIMMS 3 chip or 9 chip ? It does make a difference.
Being an OEM board w/o a manual can make it very hard to decode... first you need to set the jumpers proper and then set the bios ram settings to match the ram+what you want.
After a quick search found this: https://theretroweb.com/motherboards/s/kaimei-kma-202f-12r
Same chipset and general layout but in AT style (not LPX like yours), good thing is the jumpers by ram and 83c203 have exact same number of jumpers. I suggest you try what it's manual says...
So those jumpers (jp14,15,16?) by 83c203 need all be jumped for 640k + 3328k Extended + 128k shadow (yes you want that). And for SIMMS you want JP8-13 to be jumped as 1-2 as in your picture.
added: If you set those jumpers by 83c203 same as picture it is wrong for 4 x 1MB simms !
In the BIOS you may need to mirror those 640k + 3328K +128k settings...
If you can post a picture of the BIOS memory settings page it would help.

Thank you for the manual, it's for sure close enough to work I think. I went through and double matched up the ram banks for JP14-16 with what the manual stated (all set to 1) and the computer kicked over to detecting 512k of memory and throwing a memory count error in bios. These are 3 chip Simm modules though and the manual specifies 9 chip, so that is probably the main issue. I will get some nine chip sticks ordered up.

The bios is very simple, just the single page with the option to turn a few things on or off and set the hard drive parameters. Shadow Ram can be switched between Disabled, System, and System+Video. I'm guessing system+video is correct for later due to the layout and installation of additional video ram I've done, so I'll switch that over once I have the new simms in hand, it's never given an error with any shadow ram setting.

Bios pic, with bonus post page.
https://imgur.com/a/HGTW1E5

Ahh ok so looking at the manual it shows 512k is with those unjumped, try them all unjumped, maybe your board is wired opposite that manual.
Another thing to try is with just Jp14 jumped and see what the bios says....
About 3 chip versus 9 chip simms: they are both parity type and can be proper for many boards but the 3 chip have a greater chip density than 9 chip. Not all early chipsets like the 3 chip simms.....but run fine on 9 chip...

I took a look and all unjumped produces 640k counted and a A20/XMS error on DOS load, with just J14 jumped it's the same result. I tried Just J15 jumped out of curiousity, and it caused the floppy drives to make much more noise then normal during the self test, but produced the same result as unjumped or just J14 memory wise.

Well, an update to this. With the correct jumper settings and EMS turned *off* I was able to get it to detect all of the installed ram. This hadn't worked before so It must have been the jumper settings. A20/XMS activated correctly in DOS as well. I still have 4 9 chip simms on the way, so I might see if they work better if I encounter any further issues. Thanks again, I'm sure I wouldn't have been able to monkey this into working if I didn't have the manual to pull from.

Great ! So which jumpers setting gave you all 4Mb ? And do you have shadow enabled?
I wonder if with the bios EMS enabled caused the A20/XMS error if jumpers were set to Shadow ram. EMS uses some UMB for the EMS page frame and maybe the bios locks out all UMB from shadow if it enabled....just guessing

Horun wrote on 2024-08-05, 00:01:

Great ! So which jumpers setting gave you all 4Mb ? And do you have shadow enabled?
I wonder if with the bios EMS enabled caused the A20/XMS error if jumpers were set to Shadow ram. EMS uses some UMB for the EMS page frame and maybe the bios locks out all UMB from shadow if it enabled....just guessing

All unjumped on jumpers 14-16 appears to be the setting for max allowable ram (whatever that may be since this is a newer board then the 202 we have a manual for). I did immediately notice that DOS or programs hang randomly while executing commands or tasks, or even before post on a reset. If I remember correctly, some boards don't like 3 chip simms because they will drop data or something of the sort and cause issues that the board isn't expecting. So I'll be slotting in the 9 chip simms to see if I can resolve that. However, the jumper and bio settings are working and it's reporting:
System Memory...640k
Extended Memory...3328k
Memory Test in Protected Mode....3968k

with dos's memory stuff initializing correctly. Checkit also sees the correct amount of ram. So progress, despite the instability.

Ahh ok thanks ! So the jumpers are reversed. Good work ! Please keep some notes on what you find and best jumper + bios settings and keep us updated.
Yes 3 chip (versus 9 chip) on many older 286 and 386 boards can cause stability issues. I had issues with 3 chip simms on my 286 board, switched to 9 chips and it has run stable ever since. Something about the chip density addressing and ras-cas stuff iirc.

Horun wrote on 2024-08-05, 01:10:

Ahh ok thanks ! So the jumpers are reversed. Good work ! Please keep some notes on what you find and best jumper + bios settings and keep us updated.
Yes 3 chip (versus 9 chip) on many older 286 and 386 boards can cause stability issues. I had issues with 3 chip simms on my 286 board, switched to 9 chips and it has run stable ever since. Something about the chip density addressing and ras-cas stuff iirc.

Alright, update. The 9 chip simms appear to have resolved the hanging issues and they successfully passed checkit's ram test and a short play session of Wolf3d. I haven't really put them through their full paces, but I'm pretty confident they are going to work just fine.

As for the jumper/motherboard information, should I just tack it on here, or make a new thread that is hopefully easier to find for people who might have the same board? I'm not really sure what best etiquette is here.

Great !! I think you keeping all the info you discover in this thread it probably best idea.
You should be able to edit this topic title to something like "KMA-232F-12S 286 motherboard Extended Ram difficulties" or "KMA-232F-12S 286 motherboard Extended Ram difficulties - SOLVED".
If you cannot edit your own topic title yet (low post count?), you can PM one of the Admins or Moderators and they can do it for you.