Usually SIMM's are labeled from 0 or 1 to 7 or 8. First four is Bank0 and the rest are Bank1 - if you look at the photo you'll see labels on the side. Fill all or only the first bank if you have 4 modules. Modules come in 256KB, 1MB or 4MB. There are even 16MB out there but you won't need them. Most common are 1MB modules and 8 pieces would total at 8MB which is quite common for a 386 computer.

Four cache chips means you have 32KB or 128KB of cache. It depends on the capacity of chips. Write the long number from the chip into Google and look for datasheet. It will tell you the size of chips. Most common are 256kb. Four of those would make (256/8*4) 128KB of cache memory. Larger the cache better the performance (up to 5%).

It seems I have 4 W24257AK-20 32Kb chips there so that makes 128kb. What I would need to do with the jumpers if I were to add another 4 of those chips to make it 256Kb?
Would the motherboard even be compatible with those 16Mb memory modules? Do you have to always fill the bank full or would you be able to put just a single 4Mb module?

You have to fill at least one bank. So 4 modules. Many 386 boards don't support 16MB modules and I for one don't see the reason why would anyone use more then 32MB on a 386 system.

When you change cache chips you have to setup the jumpers accordingly.

But if I don't have a manual for the motherboard, would I just randomly change the jumpers until I hit the right one?

If you google images of this board you'll see the jumpers for 256KB cache. Jumpers seems to be near the cache chips.

https://www.google.si/search?q=KMC+A419-8&cli … iw=1598&bih=991

Also check the TAG chip. It should be 256 also.

Only image with all the cache slots full seem to be that image on that German site, but it doesn't have any jumpers set near the cache chips.
Which one is the tag chip and how do you know if it is 256?

This is how different mine looks like compared to that German site.

Baoran wrote on 2017-04-20, 21:14:

Not having any manual for this motherboard, what is usually the max 30pin memory module size that 386 motherboards accept? Is it […]
Show full quote

Not having any manual for this motherboard, what is usually the max 30pin memory module size that 386 motherboards accept?
Is it always when 386 has 8 slots for ram that it has 2 banks each having 4 slots? Is the first bank usually the slots that are closer to the ISA slots?
This german page is the only web page that I have been able to find about this motherboard http://www.amoretro.de/2013/01/kmc-a419-8-ace … otherboard.html
I would appreciate any information on how to configure this motherboard in general also. Mine only has 4 cache chips installed.

Did you have luck with RAM? I have same motherboard KMC-A419-8 VER 1.0. For example System Commander (boot loader and partition manager) requires at least 32MB RAM to perform partition operations. Sometime even more.

cyberluke wrote on 2021-06-30, 19:05:

Baoran wrote on 2017-04-20, 21:14:

Not having any manual for this motherboard, what is usually the max 30pin memory module size that 386 motherboards accept? Is it […]
Show full quote

Not having any manual for this motherboard, what is usually the max 30pin memory module size that 386 motherboards accept?
Is it always when 386 has 8 slots for ram that it has 2 banks each having 4 slots? Is the first bank usually the slots that are closer to the ISA slots?
This german page is the only web page that I have been able to find about this motherboard http://www.amoretro.de/2013/01/kmc-a419-8-ace … otherboard.html
I would appreciate any information on how to configure this motherboard in general also. Mine only has 4 cache chips installed.

Did you have luck with RAM? I have same motherboard KMC-A419-8 VER 1.0. For example System Commander (boot loader and partition manager) requires at least 32MB RAM to perform partition operations. Sometime even more.

I have not done anything with that motherboard since that. I found a different 386 motherboard that I used to build my 386 pc. I do still have it in storage though.

BTW I did the socket mod on this MB as mine has soldered Am386DX and I wanted also use PGA CPUs like my Tx486DLC that is supported in BIOS. I use FLT# pin of onboard CPU to disable it via jumper so I can switch back. I also populated 256kB cache, I had to jumper it by trial-error to be recognized by BIOS. Now I make it working with PATA SSD and installed Win95 there, it runs surprisingly well 😀
http://rayer.g6.cz/hardware/retropc2.htm