Hmm only seen two other Inswell boards and seems they were a very short lived company and never had a website AFAIK. Can not find any info on that board or much on the company so far.
You do know your board is very limited with max of 256k of onboard ram and being only a 5Mhz XT ? Odd design with the ground shields around certain sections...
added: And more weird is the SW2 block but no SW1 anywhere, never seen that on an XT until now...

The yellow wires are interesting, too. I haven't seen this before.
They could be grounding wires, maybe, to insulate the different sections of the board from each others (against RF noise etc).

The through-hole section on the lower right is interesting, too.
It's as if the space was intentionally there, to allow for fixes or custom circuits.

As for the 256KB limit, that's interesting.
That would mean the board is from the days of MS-DOS 2.x, the early 80s, when users had less than 512KB of RAM.

Anyway, it's no problem. These days, there are memory boards available.
Like that 1 MB Lo-Tech card and its clones.

(Back in the 80s/early 90s, such RAM expansion cards did already exist, too, but were less being known.
The c't magazine had a do-it-yourself project that essentially was like a Lo-Tech card.)

This motherboard have 640kb RAM but it is not turbo XT (so only 4,7MHz). The most interresting are soldered metal jumpers but without manual I don't know what are they doing. I also checked that this computer don't want to work with 16bit ISA VGA card. My other XT is working with the same card. When I replaced BIOS with the one from other XT VGA started to work so the problem is inside the BIOS.

You are correct about it being 640k, I misread the hitachi dips (my bad eyes) and thought there was 4 rows of 64k.....
The rom separation, rom range and rom timing most likely has to do with the option rom sockets....just a guess.
added: does that rom say "Z-NIX by D&A" ? Is that the original ?

Hi
Yes, sticker on this ROM IC is "Z-NIX BIOS by D&A" and it is original. Does it matter?