PBA number indicates the 300-SX20 board.

Have a look at this service manual (search for Analyzer 300SX-20) for some basic info

Yep it has like three pages with jumpers description only.
It seem to work with 545 (520) MB hdd, does this mean it will work with 2GB CF card?

This is an extract from Intels 1992 'Users Literature Catalogue' listing the documents which might be worth trying to track down

System 300SX 6/2/4/2 ==================== Intel386 Microcomputer Model 300SX-20 User's Guide____________________505090-001 Intel […]
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System 300SX 6/2/4/2
====================
Intel386 Microcomputer Model 300SX-20 User's Guide____________________505090-001
Intel386 Microcomputer Model 300SX User's Guide_______________________501329-001
Intel386 Microcomputer Model 300SX User's Guide Supplement_____________511647-001
Intel386 Microcomputer Model 300SX System Technical Reference Manual____459940-001
386 Microcomputer Model 300SX Board Technical Reference Manual_________459941-001

Maybe they've been saved somewhere as part of our Intel archiving drive - anyone?

Not sure how much, but it has cache.

The board developed the broken image symptoms
Any idea what it could be? It works fine with external VGA card.
I already replaced the Video DRAM chips but it did not help

since this is common video chip part you could buy wd video card with same part number from ebay and swap this one that you do have hot air station?

Cheers,

I have an annoying Pentium Intel board which somehow has pinout for a turbo light, but they decided to leave out the pinout for the button. Idiots. Anyway on that system the only way to toggle it is control alt + or -. The case's turbo button of course doesn't do anything =/

I doubt your board does it but that was Intel's scheme for a while.

Ordered the WD chip on eBay already.
Is there a program that can verify video memory?
I just want to ensure that the ram is okay before I replace the GPU chip

if you find more info, let us know:
https://www.ultimateretro.net/en/motherboards/10506

this is its predecessor:
https://www.ultimateretro.net/en/motherboards/10504
with a different chipset/video but it gives an idea of what its capable of.